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Scientific Data Documentation
Access To Care File, 1996
DSN: CC37.NHIS96.ACCESSX 1996 National Health Interview Survey (NHIS) Access to Care Final Public Use Data File 1. The 1996 National Health Interview Survey (NHIS) Access data file contains a variety of data items addressing access to health care services. These data items are identical to the 1995 Access data items. As a result of a Federal government furlough, two weeks of data collection were omitted in January of 1996. In addition, in order to test the changing NHIS core questionnaire, for much of the year the sample was split between the old (paper) and the new (computerized) versions of the core questionnaire. This data file includes only data obtained from the paper version of the NHIS questionnaire. The sample size is considerably smaller than in the previous year (63,402 vs. 102,467). The weights have been adjusted for these factors to produce national estimates, however, there may be a minor seasonal effect which is not corrected by the weighting. 2. The 1996 Access supplement was administered for the full year (except as mentioned above) in all of the NHIS sample households interviewed with the old paper core using three-quarters of the sample households from January-June and one-half of the sample households from July-December. Information was collected from a household respondent about all family members who participated in the NHIS. The 1996 Access file is structured in the following way: a. The NHIS person record from the core questionnaire (locations 1-335) b. The weight fields (locations 201-236) c. Fields needed for calculating variances (locations 337-358) d. Data from supplement (locations 401-439) Note: All data from the Access supplement have been shifted to start in location 401 in order to accommodate a longer public use person record required by the new sample design in 1995. 3. In 1996, two types of item non-response were identified: (1) "Not ascertained" (codes 8, 98, or 998) includes blanks when there should have been a response or when an impos- sible code appeared and; (2) Responses of "don't know" or "refused" when the question was asked (codes 9, 99 and 999). 4. The overall response rate for the 1996 Access was 90.0 per- cent. This response rate was calculated as follows: Household response rate from core of 93.8 percent multiplied by 95.9 percent who responded to the Access section yields an overall response rate of 90.0 percent. Dummy records were created for those with no response to the entire section (see file location 400). 5. Weights and variances: Since the NHIS uses a multistage sample design to represent the civilian non-institutionalized population of the United States, weights must be used to make accurate estimates based on data from the National Health Interview Survey. A set of weights are included on the 1996 file: The first weight listed below (i.e. the Final Basic Weight) will be used in most analyses of the Access data. The Final Basic Weight (location 219-227) is the equivalent of the Annual Final Basic Weight found on the NHIS Person Record of the Basic Health and Demographic component of the survey (i.e. the Core questionnaire). A national estimate of all person level variables can be made using this weight. This weight will be used in conjunction with Access data items in file locations 401-439. The Final Quarter Basic Weight before age-sex-race/ethnicity adjustment (loc. 172-177) is required by some software packages for variance estimation for surveys with complex sample designs. This weight is also included on the file. As mentioned above, the sample design for the NHIS was changed for 1995. Data from 1995 and 1996 can be combined with data from previous years, however, variances for 1995 and 1996 must be calculated separately from variances of previous years. In addition, because of the smaller sample size in 1996, some of the design elements were combined for reasons of confidentiality. The exact changes are included in the explanation below. There are a number of computer programs that yield variance estimates for data based on complex sample surveys. Some are based on replication approaches and others are based on Taylor linearization approaches. In addition to the Final Quarter Basic Weight before age-sex-race/ethnicity adjustment (which is the weight prior to post-stratification), included on the Access file is the substratum for variance estimation (loc. 342-343), the secondary sampling unit (loc. 344-350), Panel 4 (loc. 352), the variance PSU for 1996 (loc. 358), the collapsed variance stratum for 1996 (loc. 354-357), and the NSR Status variable for 1996 (loc. 353) to permit the analyst the capability of using such variance estimation procedures. These variables and weights are necessary for directly calculating sampling variances. 6. Estimating annual numbers of events or conditions a. To reduce respondent error, the recall period for questions about some events is limited to two weeks. These events are: bed days and other restricted activity days, work loss and school loss days, and doctor visits. The two-week variables are found in locations 98-107 and 120-121. Estimates of the total number of occurrences of these events in the population can be derived as follows: Number of events x 26 (number of two-week periods in a year) x Final Basic Weight = Total number of events occurring in the population during the annual period, i.e. 1996. Example: Number of bed days (Loc. 100-101) x 26 x Final Basic Weight (Loc. 219-227) = total number of bed days reported for the population in 1996. b. The recall period for acute incidence conditions is also two weeks and a national estimate of the total number of acute incidence conditions is calculated using the same procedures as for two-week events for the annual period. Number of acute incidence conditions x 26 x Final Basic Weight = Total number of acute incidence conditions occurring in the population during 1996. Note: An acute incidence condition is an acute condition with onset during the two weeks preceding the date of interview. c. The recall period for information on hospitalizations is 12 months. However, in calculating number of discharges (Locations 132-133, 137-138), only discharges occurring in the past 6 months are counted. Therefore, the weighted estimates must be calculated as follows: Number of discharges x 2 x Final Basic Weight = Total number of discharges occurring in the population in 1996. 7. Calculation of rates for events and conditions: The number of events or conditions estimated for the population, as described in item 6, above, can be used as the basis for calculating rates of occurrence of these events (or conditions) per person and per 100 persons for the total U.S. population and for various population subgroups. Note: Only rates can be estimated from these data. The percent of the population experiencing a particular type of event during the data year cannot be estimated. (The percent of the population experiencing the event in the reporting period (i.e. two weeks or 6 months) can be estimated but is generally not meaningful.) 8. Data on hospital episodes and days, based on a 12-month recall are in locations 122-131. The Final Basic Weight is used for calculating estimates of these events in the same way it is used for all other person-based variables. These variables do permit estimating the percent of the population in this annual period experiencing a hospital episode in the past year and the percent of that population having a specified number of hospital days. 9. Guidelines for Citation of Data With the goal of mutual benefit, the National Center for Health Statistics (NCHS) requests that recipients of data files cooperate in certain actions related to their use. Any published material derived from the data should acknowledge NCHS as the original source. The suggested citation to appear at the bottom of all tables is as follows: Source: National Center for Health Statistics (1996) When cited in a bibliography, the suggested citation should read: National Center for Health Statistics (1998). Data File Documentation, National Health Interview Survey of Access to Care, 1996 (machine readable data file and documentation), National Center for Health Statistics, Hyattsville, Maryland. The published material should also include a disclaimer that credits any analyses, interpretations, or conclusions reached to the author (recipient of the data file) and not to NCHS, which is responsible only for the initial data. Consumers who wish to publish a technical description of the data should make a reasonable effort to insure that the description is not inconsistent with that published by NCHS. AC-1 1996 NATIONAL HEALTH INTERVIEW SURVEY (NHIS) ACCESS TO CARE PUBLIC USE FILE Outline of Items and Codes 63,402 Records ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 1-2 - RECORD TYPE 63,402 70. Access to Care Supplement ______________________________________________________________________ 3-4 HH-2 PROCESSING YEAR 63,402 96. 1996 ______________________________________________________________________ 5-14 Recode - HOUSEHOLD ID ______________________________________________________________________ 15-16 - - PERSON NUMBER ______________________________________________________________________ 17-18 - - BLANK (Record Serial Number on some other record types) ______________________________________________________________________ 19-20 - SAMPLING WEEK CODE (Numbered within quarter) 3,680 01. Week 1 3,422 02. Week 2 5,414 03. Week 3 4,966 04. Week 4 5,009 05. Week 5 4,867 06. Week 6 5,512 07. Week 7 5,183 08. Week 8 5,390 09. Week 9 4,992 10. Week 10 4,714 11. Week 11 5,128 12. Week 12 5,125 13. Week 13 ______________________________________________________________________ AC-2 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 21 Recode LATE INTERVIEW (OR LAST ATTEMPT) FLAG 36,891 0. Interview not late 18,591 1. One week late 6,372 2. Two weeks late 1,548 3. Unknown ______________________________________________________________________ 22-23 HH-11c,d TYPE OF LIVING QUARTERS: Housing Unit = (00-07) 1,234 00. Housing unit; kind unknown 58,363 01. House, apartment, flat 37 02. HU in nontransient hotel, motel, etc. 5 03. HU-permanent in transient hotel, motel, etc. 20 04. HU in rooming house 3,072 05. Mobile home or trailer with no permanent room added 450 06. Mobile home or trailer with one or more permanent rooms added 51 07. HU not specified above Other Unit = (08-13) 39 08. Quarters not HU in rooming or boarding house 3 09. Unit not permanent in transient hotel, motel, etc. 14 10. Unoccupied site for mobile home, trailer, or tent 90 11. Student quarters in college dormitory 24 12. Other unit not specified above 0 13. Other unit; kind unknown ______________________________________________________________________ 24 HH-12a HAS TELEPHONE 57,080 1. Yes, phone number given 2,558 2. Yes, no phone number given 3,099 3. No 665 4. Unknown ______________________________________________________________________ 25 A-1 SEX 30,358 1. Male 33,044 2. Female ______________________________________________________________________ AC-3 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 26 - AGE IMPUTED FLAG 63,400 0. Age known 2 1. Age unknown, imputed as 34 ______________________________________________________________________ 27-28 Person AGE Column 976 00. Under 1 year 62,241 01-89. Number of years 185 90. 90+ years old ______________________________________________________________________ 29 Recode AGE RECODE #1 4,918 1. Under 5 years 13,210 2. 5-17 years 5,568 3. 18-24 years 19,974 4. 25-44 years 12,598 5. 45-64 years 2,213 6. 65-69 years 1,928 7. 70-74 years 2,993 8. 75 years and over ______________________________________________________________________ 30 Recode AGE RECODE #2 6,008 1. Under 6 years 11,219 2. 6-16 years 6,469 3. 17-24 years 9,603 4. 25-34 years 10,371 5. 35-44 years 7,673 6. 45-54 years 4,925 7. 55-64 years 4,141 8. 65-74 years 2,993 9. 75 years and over ______________________________________________________________________ 31-32 Recode AGE RECODE #3 2,905 00-35. Months 60,497 36. Over 3 years old ______________________________________________________________________ 33 - MONTH OF BIRTH IMPUTED FLAG 60,272 0. Month known 3,090 1. Month unknown, '8' imputed 40 9. Date of birth unknown ______________________________________________________________________ AC-4 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 34-39 A-3 - MONTH AND YEAR OF BIRTH 34-35 Month 01. January 08. August 02. February 09. September 03. March 10. October 04. April 11. November 05. May 12. December 06. June 99. Unknown 07. July 36-39 Year of Birth 168 1905. 1905 and before 63,194 1906-1997. 1906-1997 40 9999. Unknown ______________________________________________________________________ 40 Recode HISPANIC ORIGIN IMPUTED FLAG 62,712 0. Hispanic origin known 690 1. Hispanic origin imputed from reference person ______________________________________________________________________ 41-42 A-6 MAIN RACIAL BACKGROUND* - Reported (see notation for locations 43-45) 46,996 01. White 9,027 02. Black/African American** 482 03. Indian (American) 325 06. Chinese 455 07. Filipino 987 15. Other API (includes Hawaiian, Korean, Vietnamese, Japanese, Asian Indian, Samoan, and Guamanian) 3,797 16. Other race (includes Eskimo and Aleut) 181 17. Multiple race 1,152 99. Unknown _____________________________________________________________________ * Some categories may be too small to analyze separately and therefore may produce unreliable estimates; in addition, counts may not agree with those produced by the Census Bureau. ** For convenience, the category 'Black/African American' will be shown as 'Black' in all observed race or race recode locations throughout the documentation. 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 43-45 Recode RACE RECODES 43 Recode 1* Persons whose Main 51,962 1. White Racial Background 9,065 2. Black (location 41-42) was 2,375 3. Other "other" or "unknown" were classified in 44 Recode 2 the following recodes by using the racial 51,962 1. White background observed 11,440 2. Non-white by the interviewer. Use of these recodes 45 Recode 3 is recommended for estimating statistics 9,065 1. Black for the groups shown 54,337 2. Non-black here. ______________________________________________________________________ 46-47 A-5 HISPANIC ORIGIN** 12 00. Multiple Hispanic 1,387 01. Puerto Rican 646 02. Cuban 3,935 03. Mexican-Mexicano 4,391 04. Mexican-American 99 05. Chicano 1,133 06. Other Latin American 1,184 07. Other Spanish 338 08. Spanish, DK type 114 09. Unknown if Spanish origin 50,163 10. Not Spanish origin ______________________________________________________________________ 48 L-7 MARITAL STATUS 14,293 0. Under 14 years old 28,314 1. Married - spouse in household 494 2. Married - spouse not in household 3,022 3. Widowed 3,475 4. Divorced 1,102 5. Separated 12,070 6. Never married 632 7. Unknown ______________________________________________________________________ *This recode is used to define race in the Current Estimates tables. **If unknown, the family reference person code was imputed. A flag indicating imputation is in loc. 40 and the relationship to reference person is in loc. 63. 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 49 L-1 VETERAN STATUS 38,331 1. Non-veteran 1,311 2. WW I and WW II 800 3. Korean War 1,715 4. Vietnam veteran 810 5. Post-Vietnam 1,070 6. Other service 163 7. Served in Armed Forces, unknown if war veteran 1,074 8. Unknown if served in Armed Forces 18,128 Blank. Under 18 years old ______________________________________________________________________ 50 L-1 ACTIVE GUARD/RESERVE STATUS FOR PERSONS ON ACTIVE DUTY IN ARMED FORCES 38,331 0. Non-veteran 363 1. All service in Guard/Reserve 740 2. Some service in Guard/Reserve 36 3. Unknown if all service in Guard/Reserve 4,159 4. No active service in Guard/ Reserve 1,645 5. Unknown if ever active member in Guard/Reserve or served in Armed Forces 18,128 Blank. Under 18 years old ______________________________________________________________________ 51-52 L-2 EDUCATION OF INDIVIDUAL - COMPLETED YEARS 2,628 00. Never attended; kindergarten only 19,974 01-11. Grades 1-11 16,207 12. Grade 12 College: 3,321 13. 1 year 4,433 14. 2 years 1,602 15. 3 years 5,424 16. 4 years 1,039 17. 5 years 2,762 18. 6 years or more 1,094 19. Unknown 4,918 Blank. Under 5 years old ______________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 53 Recode EDUCATION OF INDIVIDUAL 2,628 0. None; kindergarten only 12,480 1. 1-8 years (elementary) 7,494 2. 9-11 years (high school) 16,207 3. 12 years (high school graduate) 9,356 4. 1-3 years (college) 5,424 5. 4 years (college graduate) 3,801 6. 5+ years (post-college) 1,094 7. Unknown 4,918 Blank. Under 5 years old ______________________________________________________________________ 54-55 - HIGHEST EDUCATION OF RESPONSIBLE ADULT FAMILY MEMBER (Detail) 151 00. Never attended; kindergarten only 9,278 01-11. Grades 1-11 20,685 12. Grade 12 College: 4,719 13. 1 year 7,364 14. 2 years 2,688 15. 3 years 9,589 16. 4 years 2,073 17. 5 years 6,048 18. 6 years or more 807 19. Unknown ______________________________________________________________________ 56 Recode HIGHEST EDUCATION OF RESPONSIBLE ADULT FAMILY MEMBER 151 0. None; kindergarten only 3,807 1. 1-8 years (elementary) 5,471 2. 9-11 years (high school) 20,685 3. 12 years (high school graduate) 14,771 4. 1-3 years (college) 9,589 5. 4 years (college graduate) 8,121 6. 5+ years (post-college) 807 7. Unknown ______________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 57 L-8 FAMILY INCOME $20,000 OR LESS 18,637 1. Less than $20,000 42,177 2. $20,000 or more 2,588 3. Unknown ______________________________________________________________________ 58-59 L-8 FAMILY INCOME 243 00. Less than $1,000 366 01. $ 1,000 - $1,999 319 02. 2,000 - 2,999 356 03. 3,000 - 3,999 433 04. 4,000 - 4,999 694 05. 5,000 - 5,999 695 06. 6,000 - 6,999 699 07. 7,000 - 7,999 701 08. 8,000 - 8,999 941 09. 9,000 - 9,999 1,132 10. 10,000 - 10,999 705 11. 11,000 - 11,999 1,304 12. 12,000 - 12,999 838 13. 13,000 - 13,999 828 14. 14,000 - 14,999 1,100 15. 15,000 - 15,999 777 16. 16,000 - 16,999 810 17. 17,000 - 17,999 1,042 18. 18,000 - 18,999 1,216 19. 19,000 - 19,999 4,786 20. 20,000 - 24,999 4,130 21. 25,000 - 29,999 4,150 22. 30,000 - 34,999 3,179 23. 35,000 - 39,999 3,180 24. 40,000 - 44,999 2,824 25. 45,000 - 49,999 15,137 26. $50,000 and over 10,817 27. Unknown ______________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 60 Recode FAMILY INCOME 1,717 0. Under $5,000 1,389 1. $ 5,000 - $ 6,999 2,341 2. 7,000 - 9,999 4,807 3. 10,000 - 14,999 4,945 4. 15,000 - 19,999 4,786 5. 20,000 - 24,999 8,280 6. 25,000 - 34,999 9,183 7. 35,000 - 49,999 15,137 8. $50,000 or more 10,817 9. Unknown ______________________________________________________________________ 61 Generated NHIS POVERTY INDEX* 48,720 1. At or above poverty threshold 8,572 2. Below poverty threshold 6,110 3. Unknown ______________________________________________________________________ 62-63 FAMILY RELATIONSHIP 62 A-2 Type of Family 6,440 &. Primary individual 684 -. Secondary individual 56,152 0. Primary family 126 1-9. Secondary family 63 A-2 Relationship to Reference Person 6,048 &. Reference person, living alone 18,770 0. Reference person, 2+ persons in household 13,756 1. Spouse, other spouse NOT in Armed Forces and living at home 151 2. Spouse, other spouse IN Armed Forces and living at home 21,000 3. Child of reference person or spouse 1,252 4. Grandchild of reference person or spouse 645 5. Parent of reference person or spouse 1,763 6. Other relative 17 7. Child of military family with no eligible reference person 0 9. DK or refused ______________________________________________________________________ *Based on family size, number of children under 18 years old and family income using the 1995 poverty levels derived from the August, 1996 Current Population Survey. 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 64 Recode FAMILY RELATIONSHIP 6,048 1. Living alone 1,076 2. Living only with non-relative 28,297 3. Living with spouse 27,981 4. Living with relative - other ______________________________________________________________________ 65-66 Generated - SIZE OF FAMILY* Unrelated individuals are coded 01 ______________________________________________________________________ 67 Generated SIZE OF FAMILY RECODE 62,665 1-8. Number of members 737 9. 9+ members ______________________________________________________________________ 68 A-2 PARENT/OTHER ADULT RELATIVE (under 25 years old and never married) 13,233 1. Both parents, no other relative 3,521 2. Mother only 324 3. Father only 1,835 4. Both parents and other 21+ year old adult relative 1,271 5. Mother and other 21+ year old adult relative 152 6. Father and other 21+ year old adult relative 281 7. No parent, but one 21+ year old adult relative 427 8. No parent, but two or more 21+ year old adult relatives 164 9. Unknown 849 0. Other 41,345 Blank. Not applicable (25+ years old or ever married) ______________________________________________________________________ *Count includes spouse in military but living at home. 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 69 B-1 MAJOR ACTIVITY (18+ years old) B-8 28,283 1. Working 7,516 2. Keeping house 2,504 3. Going to school 6,513 4. Something else 458 5. Unknown 18,128 Blank. Not applicable (under 18 years old) ______________________________________________________________________ 70 G-4 HEALTH STATUS 22,720 1. Excellent 18,116 2. Very Good 15,237 3. Good 4,899 4. Fair 1,697 5. Poor 733 6. Unknown ______________________________________________________________________ 71 Recode ACTIVITY LIMITATION STATUS*- (all ages) 3,018 1. Unable to perform major activity 3,343 2. Limited in kind/amount major activity 2,727 3. Limited in other activities 54,314 4. Not limited (includes unknowns) ______________________________________________________________________ 72 Recode ACTIVITY LIMITATION STATUS MEASURED BY "ABILITY TO WORK" (18-69 years old) 2,829 1. Unable to work 1,765 2. Limited in kind/amount of work 1,490 3. Limited in other activities 34,269 4. Not limited (includes unknowns) 23,049 Blank. Not applicable (under 18 years old, 70+ years old) ______________________________________________________________________ *This location is used to categorize persons with limitation of activity in the Current Estimates tables. 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 73 B-11 LIMITATION OF SCHOOL ACTIVITIES (5-17 years old) 81 1. Unable to attend school 438 2. Attends special school/classes 74 3. Needs special school/classes 124 4. Limited in school attendance 282 5. Limited in other activities 12,211 6. Not limited (includes unknowns) 50,192 Blank. Not applicable (under 5 years old or 18+ years old) ______________________________________________________________________ 74 B-14 NEEDS HELP WITH PERSONAL CARE (5-59 years old and limited, or 60-69 years old) 408 1. Unable to perform personal care needs 822 2. Limited in performing other routine needs 8,488 3. Not limited in performing personal or routine needs 404 4. Unknown 53,280 Blank. Not applicable (under 5 years old; 5-59 years old not limited; 70+ years old) _________________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 75 D-1 EMPLOYMENT STATUS IN PAST 2 WEEKS (18+ years old) In the Labor Force: (1-7) Currently employed: (1-3) 28,767 1. Worked in past 2 weeks 494 2. Did not work, has job; not on lay-off and not looking for work 28 3. Did not work, has job; looking for work Unemployed: (4-7) 93 4. Did not work, has job; on lay-off 6 5. Did not work, has job; on lay-off and looking for work 200 6. Did not work, has job; unknown if looking or on lay-off 960 7. Did not work, has no job; looking for work or on lay-off 14,726 8. Not in Labor Force (18+ years old) 18,128 Blank. Not applicable (under 18 years old) _________________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 76 L-6 CLASS OF WORKER 14,726 0. Not in labor force 21,596 1. Private company 756 2. Federal Government employee 1,388 3. State Government employee 2,369 4. Local Government employee 789 5. Incorporated business 2,615 6. Self-employed 29 7. Without pay 35 8. Never worked 971 9. Unknown 18,128 Blank. Under 18 years old _________________________________________________________________________ 77-79 - BLANK _________________________________________________________________________ 80-81 Recode - INDUSTRY RECODE 1 SEE APPENDIX B _________________________________________________________________________ 82-83 Recode - INDUSTRY RECODE 2 SEE APPENDIX B _________________________________________________________________________ 84-86 - BLANK _________________________________________________________________________ 87-88 Recode - OCCUPATION RECODE 1 SEE APPENDIX C _________________________________________________________________________ 89-90 Recode - OCCUPATION RECODE 2 SEE APPENDIX C _________________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 91 L-R RESPONDENT FOR CORE QUESTIONS 27,761 1. Self (entirely) 3,242 2. Self (partly) 31,712 3. Proxy 687 4. Unknown ________________________________________________________________________ 92 Recode CONDITION LIST ASSIGNED AND ASKED 10,548 1. Condition List 1, Skin and musculoskeletal 10,568 2. Condition List 2, Impairments 10,388 3. Condition List 3, Digestive 10,472 4. Condition List 4, Miscellaneous 10,113 5. Condition List 5, Circulatory 10,575 6. Condition List 6, Respiratory 738 7. Unknown _________________________________________________________________________ 93-94 G-5 HEIGHT WITHOUT SHOES (18+ years old) 363 58. 58 inches or less 43,782 59-76. Number of inches 246 77. 77 inches or more 883 99. Unknown 18,128 Blank. Under 18 years old _________________________________________________________________________ 95-97 G-5 WEIGHT WITHOUT SHOES (18+ years old) 288 097. 97 pounds or less 42,919 098-289. Number of pounds 320 290. 290 pounds or more 1,747 999. Unknown 18,128 Blank. Under 18 years old _________________________________________________________________________ 98-99 Recode TOTAL RESTRICTED ACTIVITY DAYS IN PAST TWO WEEKS 57,092 00. None 6,310 01-14. Days _________________________________________________________________________ 100-101 D-4 BED DAYS IN PAST TWO WEEKS 59,733 00. None 3,669 01-14. Days _________________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 102-103 D-2 WORK-LOSS DAYS IN PAST TWO WEEKS 61,810 00. None 1,592 01-14. Days _________________________________________________________________________ 104-105 D-3 SCHOOL-LOSS DAYS IN PAST TWO WEEKS 62,431 00. None 971 01-14. Days _________________________________________________________________________ 106-107 D-6 OTHER DAYS OF RESTRICTED ACTIVITY IN PAST TWO WEEKS 60,449 00. None 2,953 01-14. Days _________________________________________________________________________ 108-110 G-2 BED DAYS IN PAST 12 MONTHS 35,920 000. None 26,460 001-365. 1-365 days 1,022 366. Unknown _________________________________________________________________________ 111 Recode BED DAYS IN PAST 12 MONTHS 35,920 0. None 20,817 1. 1-7 days 4,084 2. 8-30 days 1,243 3. 31-180 days 316 4. 181-365 days 1,022 5. Unknown _________________________________________________________________________ 112-114 G-3 DOCTOR VISITS IN PAST 12 MONTHS 15,335 000. None 47,627 001-996. Visits 0 997. 997+ visits 440 998. Unknown _________________________________________________________________________ 115 G-3 INTERVAL SINCE LAST DOCTOR VISIT 182 0. Never 48,478 1. Less than 1 year 6,010 2. 1 to less than 2 years 4,842 3. 2 to less than 5 years 2,128 4. 5 years or more 1,762 5. Unknown _________________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 116-117 Generated - NUMBER OF CONDITIONS _________________________________________________________________________ 118-119 Generated - NUMBER OF ACUTE INCIDENCE CONDITIONS _________________________________________________________________________ 120-121 Generated - NUMBER OF TWO-WEEK DOCTOR VISITS _________________________________________________________________________ 122-123 Generated - NUMBER OF SHORT-STAY HOSPITAL EPISODES IN PAST 12 MONTHS _________________________________________________________________________ 124-126 Generated - SHORT-STAY HOSPITAL EPISODE DAYS IN PAST 12 MONTHS _________________________________________________________________________ 127-128 Generated - NUMBER OF SHORT-STAY HOSPITAL EPISODES IN PAST 12 MONTHS EXCLUDING DELIVERY* _________________________________________________________________________ 129-131 Generated - SHORT-STAY HOSPITAL EPISODE DAYS IN PAST 12 MONTHS EXCLUDING DELIVERY* _________________________________________________________________________ 132-133 Generated - NUMBER OF SHORT-STAY HOSPITAL DISCHARGES IN PAST 6 MONTHS _________________________________________________________________________ 134-136 Generated - NUMBER OF DAYS IN SHORT-STAY HOSPITAL IN PAST 12 MONTHS FOR DISCHARGES IN PAST 6 MONTHS _________________________________________________________________________ 137-138 Generated - NUMBER OF SHORT-STAY HOSPITAL DISCHARGES IN PAST 6 MONTHS EXCLUDING DELIVERY* _________________________________________________________________________ 139-141 Generated - NUMBER OF DAYS IN SHORT-STAY HOSPITAL IN PAST 12 MONTHS FOR DISCHARGES IN PAST 6 MONTHS EXCLUDING DELIVERY* _________________________________________________________________________ *Based on operation codes and reason entered hospital 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 142-143 - BLANK _________________________________________________________________________ 144 L-9b YEARS LIVED IN STATE OF PRESENT RESIDENCE 1,766 1. Less than 1 year 5,762 2. 1 yr., less than 5 yrs. 6,429 3. 5 yrs., less than 10 yrs. 5,243 4. 10 yrs., less than 15 yrs. 32,468 5. 15 years or more 3,051 9. DK refused 8,683 Blank. Not applicable (foreign born) _________________________________________________________________________ 145 L-9c YEARS LIVED IN UNITED STATES 274 1. Less than 1 year 1,339 2. 1 yr., less than 5 yrs. 1,667 3. 5 yrs., less than 10 yrs. 1,144 4. 10 yrs., less than 15 yrs. 3,997 5. 15 years or more 262 9. DK refused 54,719 Blank. Not applicable (U.S. born) _________________________________________________________________________ 146-171 - - BLANK _________________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 172-177 - - FINAL QUARTER BASIC WEIGHT BEFORE AGE-SEX-RACE/ETHNICITY ADJUSTMENT (has one implied decimal) _________________________________________________________________________ 178 SAMPLING QUARTER 16,902 1. Quarter 1 19,814 2. Quarter 2 13,470 3. Quarter 3 13,216 4. Quarter 4 ______________________________________________________________________ 179-181 - - BLANK ______________________________________________________________________ 182 Unit Control REGION File 12,500 1. Northeast 13,606 2. Midwest 21,982 3. South 15,314 4. West ______________________________________________________________________ 183 Unit Control GEOGRAPHIC DISTRIBUTION File MSA Size 8,007 1. 5,000,000 or more 7,914 2. 2,500,000 - 4,999,999 15,124 3. 1,000,000 - 2,499,999 6,747 4. 500,000 - 999,999 7,811 5. 250,000 - 499,999 4,520 6. 100,000 - 249,999 810 7. Under 100,000 12,469 Blank. Non-MSA ______________________________________________________________________ 184-185 - - BLANK ______________________________________________________________________ 186 Unit Control MSA - NON-MSA RESIDENCE File 20,826 1. In MSA; in Central City 30,107 2. In MSA; not in Central City 12,469 3. Not in MSA ______________________________________________________________________ 187-189 - - BLANK ______________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 190-200 - - CHRONIC CONDITION PREVALENCE AND INCIDENCE FACTOR (XX.XXXXXXXXX) - character format with implied decimal _________________________________________________________________________ FINAL BASIC WEIGHT 201-209 - - QUARTER 210-218 - - SEMI-ANNUAL (QUARTER/2) 219-227 - - ANNUAL (QUARTER/4) _________________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes _______________________________________________________________________ 6.5 WEIGHT 228-236 - - QUARTER, SEMI-ANNUAL AND ANNUAL* _________________________________________________________________________ ESTIMATED RESTRICTED ACTIVITY DAYS IN PAST 2 WEEKS 237-245 - - QUARTER, SEMI-ANNUAL AND ANNUAL* _________________________________________________________________________ ESTIMATED BED DAYS IN PAST 2 WEEKS 246-254 - - QUARTER, SEMI-ANNUAL AND ANNUAL* _________________________________________________________________________ ESTIMATED WORK-LOSS DAYS IN PAST 2 WEEKS 255-263 - - QUARTER, SEMI-ANNUAL AND ANNUAL* _________________________________________________________________________ ESTIMATED SCHOOL-LOSS DAYS IN PAST 2 WEEKS 264-272 - - QUARTER, SEMI-ANNUAL AND ANNUAL* _________________________________________________________________________ ESTIMATED DOCTOR VISITS IN PAST 12 MONTHS 273-281 - - QUARTER 282-290 - - SEMI-ANNUAL 291-299 - - ANNUAL _________________________________________________________________________ ESTIMATED SHORT-STAY HOSPITAL EPISODE DAYS IN PAST 12 MONTHS 300-308 - - QUARTER 309-317 - - SEMI-ANNUAL 318-326 - - ANNUAL _________________________________________________________________________ 327-335 - - ANNUAL ESTIMATED NUMBER OF SHORT-STAY HOSPITAL EPISODES IN PAST 12 MONTHS _________________________________________________________________________ * Estimates can be made for these periods depending on whether one quarter, two quarters or all four quarters of records are used. 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 336 - - BLANK ______________________________________________________________________ 337-340 Recode - STRATUM FOR VARIANCE ESTIMATION ______________________________________________________________________ 341 Recode - PSU FOR VARIANCE ESTIMATION ______________________________________________________________________ 342-343 Recode - SUBSTRATUM FOR VARIANCE ESTIMATION ______________________________________________________________________ 344-350 Generated - SECONDARY SAMPLING UNIT ______________________________________________________________________ 351 Unit Control TYPE OF PSU File 41,421 1. Self representing 21,981 2. Non self representing ______________________________________________________________________ 352 Unit Control PANEL 4 File 63,402 1-4. Code used to identify nationally representative subsamples ______________________________________________________________________ 353 - NSR STATUS VARIABLE ______________________________________________________________________ 354-357 - COLLAPSED VARIANCE STRATUM ______________________________________________________________________ 358 - VARIANCE PSU ______________________________________________________________________ 359-399 - - BLANK ______________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 400 Recode DUMMY RECORD FLAG 2,586 1. Dummy record for locations 401-440 60,816 Blank. Not a dummy record ______________________________________________________________________ 401 1a IS THERE USUAL PERSON/ PLACE FOR MEDICAL CARE 52,922 1. Yes 7,353 2. No 186 3. More than one 2,722 8. Not ascertained 219 9. DK or refused ______________________________________________________________________ 402 1b ONE PLACE MOST OFTEN (Has more than one usual person or place Q 1a = 3) 127 1. Yes 47 2. No 10 8. Not ascertained 2 9. DK or refused 63,216 Blank. NA ______________________________________________________________________ 403-404 2 MAIN REASON NO USUAL SOURCE 289 01. Two or more usual doctors/places 3,377 02. Doesn't need doctor 244 03. Doesn't like/trust/ believe in doctors 140 04. Doesn't know where to go 469 05. Previous doctor not available/moved 1,689 06. No insurance/can't afford it 6 07. Speaks different language 32 08. No care available/ not convenient 512 09. Changed residence 327 10. Other reason 261 98. Not ascertained 66 99. DK or refused 55,990 Blank. NA - Has/don't know if has one usual source of care ______________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 405 3a ONE PLACE MOST OFTEN (Q 1a = 2 and Q 2 = 01) 97 1. Yes 74 2. No 68 8. Not ascertained 3 9. DK or refused 63,160 Blank. NA ______________________________________________________________________ 406 3b PLACE FOR PREVENTIVE CARE (Q 1a = 2 and Q 2 = 01 and Q 3a NE 1) 81 1. Yes 84 2. No 22 3. Not ascertained 5 4. DK or refused 63,210 Blank. NA ______________________________________________________________________ 407 4a GO ANY PLACE IN PAST 12 MONTHS FOR MEDICAL CARE 2,728 1. Yes 4,464 2. No 2,912 8. Not ascertained 152 9. DK or refused 53,146 Blank. NA - Has a usual source of care ______________________________________________________________________ 408-409 4b KIND OF PLACE 355 01. Hospital emergency room 210 02. Urgent care/walk-in clinic 1,118 03. Doctor's office 479 04. Clinic 164 05. Health center 139 06. Hospital outpatient clinic 84 07. HMO/Prepaid group 39 08. Military or VA health care facility 92 09. Some other place 23 98. Not ascertained 25 99. DK or refused 60,674 Blank. NA ______________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 410 4c WOULD STILL GO TO PLACE (Does not have a usual source of care, care but did go to a place for medical care sometime in the past 12 months, Q 4a = 1) 1,462 1. Yes 991 2. No 23 8. Not ascertained 252 9. DK or refused 60,674 Blank. NA ______________________________________________________________________ 411-412 4d MAIN REASON WOULD NOT USE PLACE NOW (Does not have a usual source of care but did go to a place for medical care sometime in the past 12 months and would not use this place now Q 4c = 2) 410 01. Changed residence/moved 24 02. Changed jobs 30 03. Employer changed insurance coverage 64 04. Former usual source not available 5 05. Owed money to former source 76 06. Dissatisfied with former source/like new source better 148 07. Medical care needs changed 14 08. Former source stopped taking insurance/coverage 199 09. Some other reason 13 98. Not ascertained 8 99. DK or refused 62,411 Blank. NA ______________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 413 Recode REGULAR SOURCE OF MEDICAL CARE 52,922 1. Single regular source 224 2. Multiple regular sources, but sees one most often 204 3. Multiple regular sources, but no one source seen most often 2,524 4. No current regular source but had a regular source sometime in the past year 4,358 5. No current regular source of care and none in past year 229 6. No current regular source and unknown if any in past year 2,722 8. Not ascertained 219 9. DK or refused ______________________________________________________________________ 414-415 5a KIND OF PLACE 759 01. Hospital emergency room 712 02. Urgent care/walk-in clinic 35,675 03. Doctor's office 7,430 04. Clinic 1,815 05. Health center 1,381 06. Hospital outpatient clinic 3,713 07. HMO/prepaid group 763 08. Military or VA health care facility 268 09. Some other place 516 98. Not ascertained 114 99. DK or refused 10,256 Blank. NA - Does not have/DK if have a usual source of care ______________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 416 5b IS THERE PARTICULAR PERSON USUALLY SEEN 44,452 1. Yes 6,290 2. No 587 8. Not ascertained 346 9. DK or refused 11,727 Blank. NA - Does not have/DK if have a usual source of care ______________________________________________________________________ 417 6a TYPE OF HEALTH PROFESSIONAL (Usually sees a particular person when goes to usual source of care. Q 5b = 1) 43,371 1. Doctor 79 2. Nurse 222 3. Nurse practitioner 180 4. Physician's assistant 43 5. Chiropractor 43 6. Some other professional 500 8. Not ascertained 14 9. DK or refused 18,950 Blank. NA ______________________________________________________________________ 418 6b TYPE OF DOCTOR (Usually sees a particular doctor when goes to usual source of care Q 6a = 1) 40,294 1. Family doctor/GP/ internist/pediatrician 1,047 2. Obstetrician/gynecologist 1,434 3. Other specialist 451 8. Not ascertained 145 9. DK or refused 20,031 Blank. NA ______________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 419 7 LAST TIME WENT TO USUAL PLACE (Has a usual place for medical care) 1,322 0. Hasn't been there yet/never 20,540 1. Less than 3 months ago 9,747 2. At least 3 months, less than 6 months ago 9,693 3. At least 6 months, less than 1 year ago 6,342 4. At least 1 year, less than 2 years ago 4,098 5. Two or more years ago 518 8. Not ascertained 886 9. DK or refused 10,256 Blank. NA ______________________________________________________________________ 420 8 SAME PLACE FOR ROUTINE CARE (Has a usual place for medical care) 50,176 1. Yes 1,793 2. No 914 8. Not ascertained 263 9. DK or refused 10,256 Blank. NA ______________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 421 Recode RELATIONSHIP BETWEEN SOURCES OF SICK AND PREVENTIVE CARE 50,176 1. Has the same usual source for sick and routine/preventive care 1,793 2. Has a usual source for sick care, but it is not usual source of routine/routine/preventive care (may include persons with no usual source of routine/preventive care) 1,177 3. Has a usual source of sick care, but unknown if has a usual source of routine/preventive care 81 4. Has two or more usual sources of sick care and has a source for routine/preventive care 84 5. Has two or more usual sources of sick care, but does not have a source for routine/ preventive care 27 6. Has two or more usual sources of sick care, but unknown if has a usual source of routine/preventive care 7,123 7. No usual source of sick care; not asked about preventive care 2,722 8. Not ascertained 219 9. DK or refused _____________________________________________________________________ 422 9 GO TO OTHER PLACE PAST 12 MONTHS (Has a usual place for medical care) 15,094 1. Yes 36,270 2. No 1,397 8. Not ascertained 385 9. DK or refused 10,256 Blank. NA ______________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 423 10b CHANGED PLACE FOR ROUTINE CARE 4,548 1. Yes 55,862 2. No 2,841 8. Not ascertained 151 9. DK or refused ______________________________________________________________________ 424-425 10d MAIN REASON FOR CHANGE LAST TIME 1,503 01. Changed residence 197 02. Changed jobs 643 03. Employer changed insurance coverage 347 04. Former usual source not available 4 05. Owed money to former source 673 06. Dissatisfied with former source/like new source better 308 07. Medical care needs changed 126 08. Former source stopped taking insurance/coverage 639 09. Some other reason 103 98. Not ascertained 5 99. DK or refused 58,854 Blank. NA - Did not/DK change usual place of medical care in past 12 months ______________________________________________________________________ 426 11b NEEDED CARE BUT NOT ABLE TO GET IT 1,703 1. Yes 58,773 2. No 2,792 8. Not ascertained 134 9. DK or refused ______________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 427-428 11d MAIN REASON DIDN'T GET CARE 801 01. Could not afford it 278 02. No insurance 32 03. Doctor did not accept Medicaid/ insurance plan 50 04. Insurance didn't cover 30 05. Not serious enough 34 06. Wait too long in clinic/office 141 07. Difficulty getting an appointment 19 08. Doesn't like/trust/ believe in doctors 33 09. No doctor available 8 10. Didn't know where to go 14 11. No way to get there 7 12. Hours not convenient 0 13. Speak a different language 1 14. Health of another family member interfered 9 15. Clinic/office not accessible 135 16. Other reason 106 98. Not ascertained 5 99. DK or refused 61,699 Blank. NA - Obtained medical care when needed during the past 12 months ______________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 429 11e LACK OF INSURANCE OR MONEY A REASON 121 1. Yes 316 2. No 102 3. Not ascertained 3 9. DK or refused 62,860 Blank. NA - Obtained medical care when needed during the 12 months or already mentioned that money or lack of insurance was a reason ______________________________________________________________________ 430 12b DELAYED SEEKING MEDICAL CARE BECAUSE OF COST 4,507 1. Yes 55,972 2. No 2,812 8. Not ascertained 111 9. DK or refused ______________________________________________________________________ 431 13b NEEDED DENTAL CARE BUT COULD NOT GET IT 4,800 1. Yes 55,603 2. No 2,833 8. Not ascertained 166 9. DK or refused ______________________________________________________________________ 432 14b NEEDED PRESCRIPTION MEDICINES BUT COULD NOT GET THEM 1,504 1. Yes 58,945 2. No 2,781 8. Not ascertained 172 9. DK or refused ______________________________________________________________________ 433 15b NEEDED EYEGLASSES BUT COULD NOT GET THEM 1,874 1. Yes 58,379 2. No 2,947 8. Not ascertained 202 9. DK or refused ______________________________________________________________________ 1996 NHIS ACCESS TO CARE PUBLIC USE FILE ______________________________________________________________________ File Locations Item No. Frequency Items and Codes ______________________________________________________________________ 434 16b NEEDED MENTAL HEALTH CARE BUT COULD NOT GET IT 348 1. Yes 60,046 2. No 2,849 8. Not ascertained 159 9. DK or refused ______________________________________________________________________ 435-436 - - BLANK ______________________________________________________________________ 437-438 Check CHECK ITEM (Reference Person Item A5 Only) PERSON WHO ANSWERED MOST QUESTIONS 865 00. Respondent not ascertained 59,837 01-28. Person number 0 30-97. Person number 101 98. Active duty military 13 99. Non household member 2,586 Blank. Dummy record ______________________________________________________________________ 439 Recode RESPONDENT FOR SUPPLEMENT STATUS 23,701 1. Self 36,319 2. Proxy 796 9. Unknown respondent 2,586 Blank. Dummy record ____________________________________________________________________ 440 - - BLANK ______________________________________________________________________ APPENDIX A There is no Appendix for this document B-1 APPENDIX B INDUSTRY RECODES OUTLINE Revised in 1995 _______________________________________________________________________________ Recodes --------------------- No. 1 No. 2 Chrs. Chrs. Industry Title SIC Code* 80-81 82-83 _______________________________________________________________________________ 01 01 AGRICULTURE 01-02,071-072,074- 076,078 02 01 FORESTRY AND FISHERIES 08-09 _______________________________________________________________________________ 10 02 MINING 10,12-14 _______________________________________________________________________________ 20 03 CONSTRUCTION 15-17 _______________________________________________________________________________ (30-34, 40-46) (04) MANUFACTURING: (30-34) NONDURABLE GOODS 30 04 Food and kindred products 201-209 31 04 Textile mill and finished 221-229,231-239 textile products 32 04 Printing, publishing and 271-279 allied industries 33 04 Chemicals and allied 281-287,289 products 34 04 Other nondurable goods 21,261-263,265,267, 291,295,299,301- 306,308,311,313- 317,319 _______________________________________________________________________________ *Standard Industrial Classification APPENDIX B INDUSTRY RECODES OUTLINE Revised in 1995 _______________________________________________________________________________ Recodes ----------------- No. 1 No. 2 Chrs. Chrs. Industry Title SIC Code* 80-81 82-83 _______________________________________________________________________________ (30-34, 40-46) (04) MANUFACTURING: - continued (40-46) DURABLE GOODS 40 04 Furniture, lumber and wood 241-245,249,25 41 04 Primary metal industries 331-332,334,3331, 3334,3339,3351, 3353-3357,3363- 3366,3369,339 42 04 Fabricated metal 341-349 industries, including ordnance 43 04 Machinery, except 351-359 electrical 44 04 Electrical machinery, 361-367,369 equipment and supplies 45 04 Transportation equipment 371-376,379 46 04 Other and not specified 321-329,381-382, durable goods 384-387,39 _______________________________________________________________________________ *Standard Industrial Classification APPENDIX B INDUSTRY RECODES OUTLINE Revised in 1995 _______________________________________________________________________________ Recodes ----------------- No. 1 No. 2 Chrs. Chrs. Industry Title SIC Code* 80-81 82-83 _______________________________________________________________________________ (50-54) (05) TRANSPORTATION, COMMUNICATIONS AND OTHER PUBLIC UTILITIES 50 05 Railroads 40 51 05 Trucking service and 421-423 warehousing 52 05 Other transportation 41,43-47 53 05 Communications 481-484,489 54 05 Utilities and sanitary 491-497 _______________________________________________________________________________ 60 06 WHOLESALE TRADE 501-509,511-519 _______________________________________________________________________________ *Standard Industrial Classification APPENDIX B INDUSTRY RECODES OUTLINE Revised in 1995 _______________________________________________________________________________ Recodes ----------------- No. 1 No. 2 Chrs. Chrs. Industry Title SIC Code* 80-81 82-83 _______________________________________________________________________________ (61-65) (07) RETAIL TRADE 61 07 General merchandise stores 531,533,539 62 07 Food, bakery and dairy 541-546,549 stores 63 07 Automotive dealers and 551-557,559 gasoline stations 64 07 Eating and drinking places 58 65 07 Other and not specified 521,523,525-527,56, retail trade 571-572,5731,5734- 5736,591-594,5961- 5963,598,5992-5995, 5999 _______________________________________________________________________________ (70-71) (08) FINANCE, INSURANCE, AND REAL ESTATE 70 08 Banking and credit 60-61 agencies 71 08 Insurance, real estate, 62-65,67 and other finance _______________________________________________________________________________ *Standard Industrial Classification APPENDIX B INDUSTRY RECODES OUTLINE Revised in 1995 _______________________________________________________________________________ Recodes ----------------- No. 1 No. 2 Chrs. Chrs. Industry Title SIC Code* 80-81 82-83 _______________________________________________________________________________ (75-85) (09-12) SERVICES: (75-76) (09) BUSINESS AND REPAIR SERVICES 75 09 Business services 731-738,751,752, 7542 76 09 Repair services 753,7549,762-764, 7692,7694,7699 (77-78) (10) PERSONAL SERVICES 77 10 Private households 88 78 10 Other personal services 701-704,721-726,729 79 11 ENTERTAINMENT AND 781-784,791-794,799 RECREATION SERVICES (80-85) (12) PROFESSIONAL AND RELATED SERVICES 80 12 Hospitals 806 81 12 Health services, except 801-803,8041-8043, hospitals 8049,805,807-809 82 12 Elementary and secondary 821-822 schools and colleges 83 12 Other educational services 823-824,829 84 12 Social services, religious 832-833,835-836, and membership 839,84,861-866,869 organizations 85 12 Legal, engineering and 81,871-874,899 other professional services _______________________________________________________________________________ *Standard Industrial Classification APPENDIX B INDUSTRY RECODES OUTLINE Revised in 1995 _______________________________________________________________________________ Recodes ---------------- No. 1 No. 2 Chrs. Chrs. Industry Title SIC Code* 80-81 82-83 _______________________________________________________________________________ 90 13 PUBLIC ADMINISTRATION 911-913,919,92-97 _______________________________________________________________________________ 95 14 UNKNOWN INDUSTRY - (Includes never worked) _______________________________________________________________________________ 96 14 REFUSED, CLASSIFIED, ETC. _______________________________________________________________________________ 97 15 NOT IN LABOR FORCE - codes Blank and 8 in current activity recode (loc. 75) (Under 18 or 18+ and not in Labor Force). _______________________________________________________________________________ 98 16 ARMED FORCES (excludes Reserves and National Guard) _______________________________________________________________________________ *Standard Industrial Classification APPENDIX B INDUSTRY RECODE TITLES _______________________________________________________________________________ Recode No. 1 Code Titles Inclusions _______________________________________________________________________________ 01 AGRICULTURE, FORESTRY AND FISHERIES 01,02 02 MINING 10 03 CONSTRUCTION 20 04 MANUFACTURING 30-34, 40-46 05 TRANSPORTATION, COMMUNICATIONS AND OTHER PUBLIC 50-54 UTILITIES 06 WHOLESALE TRADE 60 07 RETAIL TRADE 61-65 08 FINANCE, INSURANCE, AND REAL ESTATE 70-71 09 BUSINESS AND REPAIR SERVICES 75-76 10 PERSONAL SERVICES 77-78 11 ENTERTAINMENT AND RECREATION SERVICES 79 12 PROFESSIONAL AND RELATED SERVICES 80-85 13 PUBLIC ADMINISTRATION 90 14 UNKNOWN (includes never worked, refused, 95-96 classified, etc.) 15 NOT IN LABOR FORCE 97 16 ARMED FORCES 98 C-1 APPENDIX C OCCUPATION RECODE OUTLINE Revised in 1995 __________________________________________________________________________ Recodes ---------------- No. 1 No. 2 Chrs. Chrs. Occupation Title SOC Code* 87-88 89-90 __________________________________________________________________________ (01-03) (01) EXECUTIVE, ADMINISTRATIVE, - AND MANAGERIAL OCCUPATIONS 01 01 Officials and administrators, 111-113 public administration 02 01 Managers and administrators, 121-128,131- except public administration 1344,1351- 1354,1359, 136-139 03 01 Management related occupations 1412,1414-1415, 1419,142-143, 1442-1443,1449, 145,1472- 1473,149 __________________________________________________________________________ *Standard Occupational Classification APPENDIX C OCCUPATION RECODE OUTLINE Revised in 1995 __________________________________________________________________________ Recodes ---------------- No. 1 No. 2 Chrs. Chrs. Occupation Title SOC Code* 87-88 89-90 __________________________________________________________________________ (04-11) (02) PROFESSIONAL SPECIALTY OCCUPATIONS - 04 02 Engineers 1622-1628,1632- 1637,1639 05 02 Architects and surveyors 161,164 06 02 Natural mathematical and 171-172,1732- computer scientists 1733,1739, 1842-1843, 1845-1847,1849, 1852-1855 07 02 Health diagnosing occupations 261-262,27,281, 283,289 08 02 Health assessment and 29,301-302, treating occupations 3031-3034,3039, 304 09 02 Teachers, librarians and 2212-2218, Counselors 2222-2228, 2231-2238, 2242-2247, 2249,231-233, 235,236,239,24, 251,252 10 02 Writers, artists, 34,321-329, entertainers and athletes 331-333,398 11 02 Other professional specialty 1912-1916, occupations 1919,192, 2032-2033, 2042,2049, 211-212 __________________________________________________________________________ *Standard Occupational Classification. APPENDIX C OCCUPATION RECODE OUTLINE Revised in 1995 __________________________________________________________________________ Recodes ---------------- No. 1 No. 2 Chrs. Chrs. Occupation Title SOC Code* 87-88 89-90 ___________________________________________________________________________ (12-13) (03) TECHNICIANS AND RELATED - SUPPORT OCCUPATIONS 12 03 Health technologists and 362-366,369 technicians 13 03 Technologists, technicians 3711-3713,3719, except health 372-373,382, 3831-3833, 384,389, 392-393,396, 3971-3972, 3974,399, 825 ___________________________________________________________________________ (14-16) (04) SALES OCCUPATIONS - 14 04 Supervisors and proprietors 40 15 04 Sales representatives, 4122-4124, commodities and finance 4152-4153, 421,423-424 16 04 Other sales 4342-4348,4351- 4354,4356,4359, 4362-4367,4369, 444-447,449 __________________________________________________________________________ *Standard Occupational Classification APPENDIX C OCCUPATION RECODE OUTLINE Revised in 1995 __________________________________________________________________________ Recodes ---------------- No. 1 No. 2 Chrs. Chrs. Occupation Title SOC Code* 87-88 89-90 ___________________________________________________________________________ (17-21) (05) ADMINISTRATIVE SUPPORT - OCCUPATIONS, INCLUDING CLERICAL 17 05 Computer equipment operators 4612-4613 18 05 Secretaries, stenographers 4622-4624 and typists 19 05 Financial records processing 4712-4713, occupations 4715-4716, 4718 20 05 Mail and message distributing 4742-4745 21 05 Other administrative support 4511-4514,4516, 4519,4521-4529, 463,4642-4645, 4649,4662-4664, 4692,4694,4696, 4699,4722-4723, 4729,4732-4733, 4739,4751-4759, 4782-4784,4786- 4787,4791-4795, 4799 22 06 Private household occupations 502-507,509 ___________________________________________________________________________ *Standard Occupational Classification. APPENDIX C OCCUPATION RECODE OUTLINE Revised in 1995 ___________________________________________________________________________ Recodes ---------------- No. 1 No. 2 Chrs. Chrs. Occupation Title SOC Code* 87-88 89-90 ___________________________________________________________________________ (23-24) (07) PROTECTIVE SERVICE OCCUPATIONS 23 07 Police and firefighters 5111-5112, 5122-5123, 5132-5134 24 07 Other protective service 5113,5142,5144, occupations 5149 ___________________________________________________________________________ (25-28) (08) SERVICE OCCUPATIONS, EXCEPT PROTECTIVE AND HOUSEHOLD 25 08 Food service 5211-5219 26 08 Health service 5232-5233,5236 27 08 Cleaning and building service 5241-5242, 5244-5246,5249 28 08 Personal service 5251-5258,5262- 5264,5269 ___________________________________________________________________________ (29-31) (09) FARMING, FORESTRY AND FISHING OCCUPATIONS 29 09 Farm operators and managers 5512-5515,5522- 5525 30 09 Farm workers and other 5611-5619, agricultural workers 5621-5622, 5624-5625,5627 31 09 Forestry and fishing 571-573,579, occupations 583-584,8241(pt.) ___________________________________________________________________________ *Standard Occupational Classification. APPENDIX C OCCUPATION RECODE OUTLINE Revised in 1995 ___________________________________________________________________________ Recodes ---------------- No. 1 No. 2 Chrs. Chrs. Occupation Title SOC Code* 87-88 89-90 ___________________________________________________________________________ (32-34) (10) PRECISION PRODUCTION, CRAFT AND REPAIR OCCUPATIONS 32 10 Mechanics and repairers 60,6111-6118, 613-614,6151- 6159,616,6171- 6179 33 10 Construction and extractive 6311-6316,6318, trades 632,6412- 6414(pt.),6422, 6424,6432-6433, 6442-6444,645, 6462-6468,6472- 6476,6479,652- 654,656 34 10 Precision production 67,71, occupations 6811-6814, 6816-6817, 6821-6824, 6829,6831-6832, 6835,6839,6844, 6852-6854,6856, 6859,6861-6862, 6864-6867,6869, 6871-6873,6879, 6881-6882,691- 696,7477(pt.), 7668,7677(pt.), 7752,828 ___________________________________________________________________________ *Standard Occupational Classification APPENDIX C OCCUPATION RECODE OUTLINE Revised in 1995 ___________________________________________________________________________ Recodes ---------------- No. 1 No. 2 Chrs. Chrs. Occupation Title SOC Code* 87-88 89-90 ___________________________________________________________________________ OPERATORS, FABRICATORS AND LABORERS (35-36) (11) MACHINE OPERATORS, ASSEMBLERS AND INSPECTORS 35 11 Machine operators and 6841-6842,6849, tenderers, except precision 6855,6863,6868, 7312-7319,7322, 7324,7326,7329, 7339,7342-7344, 7349,7431-7435, 7439,7443-7444, 7449,7451-7452, 7459,7462-7463, 7467,7472,7474, 7476-7478,7479, 7512-7519,7522, 7529,7539,7542- 7544,7549,7631- 7636,7639,7642- 7644,7649,7651- 7652,7654-7659, 7661-7667,7669, 7671-7676, 7677(pt.), 7678-7679 36 11 Fabricators, assemblers, 7332-7333,7532- inspectors and samplers 7533,7714,7717, 72,774,7753- 7759,782-785,787 ___________________________________________________________________________ *Standard Occupational Classification APPENDIX C OCCUPATION RECODE OUTLINE Revised in 1995 ___________________________________________________________________________ Recodes ---------------- No. 1 No. 2 Chrs. Chrs. Occupation Title SOC Code* 87-88 89-90 ___________________________________________________________________________ (37-39) (12) TRANSPORTATION AND MATERIAL MOVING OCCUPATIONS 37 12 Motor vehicle operators 8111,8212-8216, 8218-8219,874 38 12 Other transportation, except 8113,8232-8233, motor vehicles 8239,8241(pt.), 8242-8245 39 12 Material moving equipment 812,8312-8319 operators ___________________________________________________________________________ (40-41) (13) HANDLERS, EQUIPMENT CLEANERS, HELPERS AND LABORERS 40 13 Construction laborers 871 41 13 Freight, stock and material 85,861-863, handlers 8641-8646, 8648,865, 8722-8726,873, 875,8761,8769 ___________________________________________________________________________ * Standard Occupational Classification APPENDIX C OCCUPATION RECODE OUTLINE Revised in 1995 ___________________________________________________________________________ Recodes ---------------- No. 1 No. 2 Chrs. Chrs. Occupation Title SOC Code* 87-88 89-90 ___________________________________________________________________________ 95 14 UNKNOWN OCCUPATION (Includes never worked) ___________________________________________________________________________ 96 14 REFUSED, CLASSIFIED, ETC. ___________________________________________________________________________ 97 15 NOT IN LABOR FORCE - codes Blank and 8 in current activity recode (Loc. 75). (Under 18 or 18+ and Not in Labor Force) ___________________________________________________________________________ 98 16 MILITARY ___________________________________________________________________________ *Standard Occupational Classification APPENDIX C OCCUPATION RECODE TITLES ___________________________________________________________________________ Recode No. 1 Code Titles Inclusions ___________________________________________________________________________ MANAGERIAL AND PROFESSIONAL SPECIALTY OCCUPATIONS 01 EXECUTIVE, ADMINISTRATIVE AND MANAGERIAL OCCUPATIONS 01-03 02 PROFESSIONAL SPECIALTY OCCUPATIONS 04-11 TECHNICAL, SALES AND ADMINISTRATIVE SUPPORT OCCUPATIONS 03 TECHNICIANS AND RELATED SUPPORT OCCUPATIONS 12-13 04 SALES OCCUPATIONS 14-16 05 ADMINISTRATIVE SUPPORT OCCUPATIONS, INCLUDING 17-21 CLERICAL SERVICE OCCUPATIONS 06 PRIVATE HOUSEHOLD OCCUPATIONS 22 07 PROTECTIVE SERVICE OCCUPATIONS 23-24 08 SERVICE OCCUPATIONS, EXCEPT PROTECTIVE AND 25-28 HOUSEHOLD 09 FARMING, FORESTRY AND FISHING OCCUPATIONS 29-31 10 PRECISION PRODUCTION, CRAFT AND REPAIR OCCUPATIONS 32-34 OPERATORS, FABRICATORS AND LABORERS 11 MACHINE OPERATORS, ASSEMBLERS AND INSPECTORS 35-36 12 TRANSPORTATION AND MATERIAL MOVING OCCUPATIONS 37-39 13 HANDLERS, EQUIPMENT CLEANERS, HELPERS AND LABORERS 40-41 14 UNKNOWN OCCUPATION (includes never worked, refused, 95-96 classified, etc.) 15 NOT IN LABOR FORCE 97 16 MILITARY 98 VARIANCE ESTIMATION FOR PERSON DATA USING THE NHIS PUBLIC USE PERSON DATA TAPE, 1995-2004 April 17, 1998 About this document: This document provides basic design information about the 1995-2004 NHIS and presents methods to compute standard errors for each annually released person- level database. This document focuses upon a full-sample NHIS Core survey that is anticipated for each data collection year. For some years the full-sample methods need to be modified to account for design changes. In particular, the 1996 NHIS has a sample design quite different from the 1995 NHIS. Also, Supplemental surveys may require modified methods. Some notes about these modifications appear at the end of this document. Contents VARIANCE ESTIMATION FOR PERSON DATA USING THE NHIS PUBLIC USE PERSON DATA TAPE, 1995 Pages 2-11 Notes for the 1995 NHIS Year 2000 supplement Page 12 Notes for the 1996 NHIS Pages 13-16 VARIANCE ESTIMATION FOR PERSON DATA USING THE NHIS PUBLIC USE PERSON DATA TAPE, 1995 Introduction: The data collected in the NHIS are obtained through a complex sample design involving stratification, clustering, and multistage sampling, and the final weights are subject to several adjustments. Any variance estimation methodology must involve numerous simplifying assumptions about the design and weighting. We provide some oversimplified conceptual NHIS design structures that should allow users of this Public Use Data Set to compute reasonably accurate standard errors. There are several available software packages for analyzing complex samples. A comparison is beyond the scope of this document, but an Internet web page Summary of Survey Analysis Software currently located at http://www.fas.harvard.edu/~stats/survey-soft/survey-soft.html provides references and discussion. At NCHS the software package SUDAAN has been used to produce standard errors. In this document SAS and SUDAAN computer code is provided, but without guarantees of any kind. The computer code and methods are subject to change without notification to the user. The entire risk as to the results and performance is assumed by the user. NCHS recommends that any analysis of NHIS data be done under the supervision of a statistician who understands the implications of complex-sample design surveys. Conceptual NHIS design for 1995 The U.S. Bureau of the Census partitions the state counties or equivalents along with metropolitan areas into a universe of about 1900 Primary Sampling Units (PSUs) (note, PSUs may be combined counties) to provide the primary sampling areas for its many national surveys. For the NHIS these universe PSUs are partitioned into geographical strata at the state level. Some of the larger universe PSUs are self- representing (SR), i.e., they are in the NHIS with certainty. The other PSUs are called non-self-representing (NSR) or non-certainty PSUs. Within each state the NSR PSUs are partitioned into strata based upon similarity of PSU characteristics. Within each NSR stratum 2 PSUs are selected using Durbin's probability proportional to size (PPS) sampling method using the population as a measure of size. (In some smaller states only 1 PSU is drawn PPS). The SR PSUs are equivalent to strata, but historically they have been referred to as PSUs. (PPS and Durbin sampling are discussed in Chapter 9A of Cochran (1977)). Within a sampled NSR or SR PSU the geography is partitioned into smaller geographical clusters which are used to form the universe of secondary sampling units (SSUs). These SSUs are then partitioned into density strata based upon black and Hispanic population concentration as determined by the 1990 Decennial Census. An additional strata for new construction since the last Decennial Census is also created. Within each density stratum SSUs are sampled at different rates to meet different design objectives. Within each sample SSU, all households containing black or Hispanic persons are sampled, while all other households are subsampled. Supplemental NHIS surveys may require additional sampling at SSU, household, or family levels. The fundamental sampling weights are created such that under ideal sampling conditions, unbiased estimators for each level of sampling are available. In practice, however, the final sampling weights are adjusted for non- response, and ratio adjusted. Furthermore, in 1995 a government shutdown resulted in three lost weeks of sample which resulted in further weighting adjustments. The most important adjustment is a quarterly post- stratification to 90 age/sex/race/ethnicity Census control totals. For variance estimation purposes, NCHS treats the NHIS as a two-stage sample. The PSU probabilities of selection are known, and the SSUs are treated as sampled with replacement within PSU density strata. Sampling weights are adjusted by postratification. With these assumptions the SUDAAN software is used to compute variances. Much of the design information, state, density strata, and Durbin probabilities can be used to identify the smaller geographical areas. NCHS forbids the disclosure of information which may compromise the confidentiality promised to survey respondents, so some design information is not provided with the Public Use Data. While all design information is not available to the public, variance estimation methods exist which provide similar results to the NCHS internally used methodology. Two methods are described below. Design Information Available on the NHIS Public Use Databases. CAUTION For 1996 databases, refer to the Notes at the end of this document. The following variables are used to produce code for variance estimation. Field locations below are from the PERSON level database, but may change on other databases; the user should check the file documentation. Variable Tape Name Location Field Label STRAT_V 337-340 'STRATA FOR VARIANCE ESTIMATION' PSU_V 341 'PSU FOR VARIANCE ESTIMATION' SUB_V 342-343 'SUBSTRATUM FOR VARIANCE ESTIMATION' SSU 344-350 'SECONDARY SAMPLING UNIT' PANEL 352 'PANEL 4' TYPE_PSU 351 'TYPE OF PSU' WTF 219-227 'FINAL BASIC WEIGHT' Two methods of variance estimation are provided. Method 1 - 187 Strata containing 2 PSUs per stratum sampled with replacement Here, the NHIS universe has been partitioned into 187 strata. Most of the original NHIS strata and PSUs retain their original sampling structure with two PSUs being sampled per stratum, but a few strata have been collapsed, and in the largest self-representing strata, two pseudo-PSUs have been created. All PSUs are treated as sampled with replacement within their respective strata. This method will provide somewhat conservative standard errors, and the standard error estimator itself has less stability than the standard error estimator described by Method 2 below. Method 1 should be applicable to many complex survey sample design computer programs which require exactly 2 sampled PSUs per stratum. This method is robust when analyzing subsetted data (See the section "Subsetted Data Analysis" below). Coding required (SAS code provided): STRATUM = STRAT_V; PSU = PANEL; IF (PSU_V = 5) THEN PSU = INT((PANEL + 1)/2); IF(PSU_V = 8) THEN STRATUM = 553; IF((TYPE_PSU = 1) AND (PSU_V IN (2,4))) THEN STRATUM = (STRAT_V -1); IF((STRAT_V = 921) AND (PSU_V = 3)) THEN STRATUM = 901; As a check the user should observe 374 PSUs when using the full database. For the above simplification of the NHIS sample design structure, the following SUDAAN design statements may be used. (Note, the input file must first be sorted by STRATUM and PSU variables.) PROC ... DESIGN = WR; NEST STRATUM PSU ; WEIGHT WTF; See the Section "Worked SUDAAN Examples" below for further discussion. Method 2 - Multiple PSUs per Stratum design sampled with replacement This method provides for more statistically efficient variance estimation than Method 1, since it makes better use of the sampling design information. Its application is limited to software that can handle multiple PSUs per stratum, e.g., SUDAAN. For this method the original certainty PSUs are partitioned by aggregations of the original race-ethnic density strata used in sampling. The first randomly sampled unit is actually the SSU variable which is now treated as the PSU variable. (Note, a certainty PSU unit contributes nothing to the variance at the PSU sampling level.) Non- certainty-strata PSUs are treated as being sampled with replacement within their respective strata. Except for a few special cases, the non-certainty PSUs have exactly the same structure in both Methods 1 and 2. Coding required, (SAS code provided ): IF TYPE_PSU = 1 THEN DO; /* certainty strata PSUs */ STRATUM = STRAT_V*1000 + SUB_V; PSU = SSU ; END; ELSE DO ; /* non-certainty PSU */; STRATUM = STRAT_V ; PSU = PSU_V ; END; As a check, the user should observe the following counts: Certainty Strata PSUs 4079 Non-certainty Strata PSUs 259 Total PSUs 4338 For the Method 2 design structure, the following SUDAAN design statements may be used. (Note, the input file must first be sorted by STRATUM and PSU variables.) PROC ... DESIGN = WR; NEST STRATUM PSU; WEIGHT WTF; See the Section "Worked SUDAAN Examples" for further discussion. CAUTION. Method 2 should only be used on a full sample person data base. Using this method with subsetted data may lead to incorrectly computed standard errors. (See the section "Subsetted Data Analysis" below). If using a subsetted data set, the user should check the degree of agreement of the certainty and non-certainty counts with the values presented above. CAUTION A typically used rule-of-thumb for degrees of freedom to associate with a standard error is the quantity (number of PSUs - number of strata). This rule assumes that the PSUs are somewhat comparable in size. For Method 2 this rule may be grossly inaccurate since the concept of PSU is quite different for certainty and non-certainty strata. Certainty strata PSUs of Method 2 have small weighted values relative to those of non-certainty PSUs. The rule-of-thumb degrees of freedom for Method 1 is 187, and Method 2 should have a "true" degrees of freedom exceeding that of Method 1. However, for practical purposes, any degrees of freedom exceeding 120 can be treated as infinite, i.e., one uses a normal Z-statistic instead of a t-statistic for testing. Note, that a one-tailed critical t0.025 at 120 degrees of freedom is 1.98 while at an infinite degrees of freedom (i.e., a z-value) is 1.96. If a variable of interest covers most of the NHIS PSUs, the limiting value would probably be adequate for analysis. The user should consult a mathematical statistician for discussion of degrees of freedom. SUBSETTED DATA ANALYSES Frequently, studies of NHIS variables are restricted to select subdomains, e.g., persons aged 65 and older. To save on storage the user may delete all records outside of the domain of interest. This procedure of keeping only select records is called subsetting the data. With a subsetted data set one can produce correct point estimates, e.g., the subdomain means, but standard errors may be computed incorrectly when using a compromised design structure. For example, if a stratum of Method 2 contains 10 PSUs and 5 are lost because of subsetting, a SUDAAN run on the subsetted data will use an incorrect formula to compute stratum contributions to the variance. If the full data are run, SUDAAN correctly handles the 5 empty PSUs. Note, that SUDAAN has a SUBPOPN option that allows the targeting of a subdomain from a full design data base. (See the SUDAAN manual for details). Subsetting methods with SUDAAN Strategy 1. Use Method 1 above with the MISSUNIT option on the NEST statement - NEST STRATUM PSU/MISSUNIT ; If a WR design has exactly 2 PSUs per stratum and some PSUs are removed from the database then the SUDAAN MISSUNIT option performs a fix-up which produces a standard error identical to that achieved when using a full data set and SUBPOPN statement. Note, other output like design effects, degrees of freedom, standardization may be computed differently. The user is responsible for checking that subsetted input leads to correct results. Strategy 2. Use Method 1 or 2 above on a "fixed-up" subsetted data set. Basically, one needs to add some dummy records containing full design information to the subsetted data set. To do this follow these instructions: 1. Create a 2-variable file containing STRATUM and PSU for each record of the full person file ( 100,000+ records ) 2. Sort this file by STRATUM and PSU within STRATUM. 3. Keep only 1 record for each PSU add WTF = 10 -10 as a very small weight add variable DUMMY = 0 to designate dummy record A file, called DESIGN containing 4 variables with 374 records ( Method 1 used) or with 4338 records (Method 2 used) is created 4. Append DESIGN to the original subsetted database, called DATASET, to form a new set, called DATANEW. Define DUMMY = 1 on the DATASET component. On the DESIGN component records define all variables other than STRATUM, PSU, WTF, DUMMY as missing ".". 5. Sort DATANEW by STRATUM PSU 6. In SUDAAN use a "SUBPOPN DUMMY = 1;" line to direct SUDAAN to restrict estimation to the subdomain of interest. With the above fix-up SUDAAN will correctly handle empty PSUs when computing the standard errors. SUDAAN output that needs the entire full sample database for correct computation, e.g., design effects, may or may not be appropriate. See the SUDAAN manual for computational forms or consult with a mathematical statistician for correct interpretation. Other notes on Subsetting data: If a subsetted database under Method 2 has only a few missing PSUs, the subsetted database can probably be run with SUDAAN without being fixed up. For example, a subsetting by SEX will most likely result in all PSUs still being in sample, but black males aged 65 and older would result in the loss of many PSUs. The impact of running SUDAAN on uncorrected subsetted data varies. Frequently, subsetted runs produce results consistent with those run on a full data set, but sometimes they do not. Subsetting by aggregates of Strata does not need a fix-up. The condition, doctor visit, and hospital record databases are actually subsetted files. To use with SUDAAN properly, the information should be linked back to the appropriate person on the person file. Some statistics, based upon aggregation of records, may be computed directly from this file along with the fix-up. Consult with a statistician for appropriate SUDAAN usage. WORKED SUDAAN EXAMPLES In the following runs the variables used are LDR = proportion of persons without a doctor visit in the last 2 years TDV_R = mean number of annual doctor visits (based upon 2 week recall) HLT_FP = proportion of persons with self-reported fair or poor health status (omitting missing) AGE2: 1 = aged less than 18 2 = aged 18 to 44 3 = aged 45 to 64 4 = aged 65 and older The following SUDAAN code was executed for both Method 1 and Method 2: Caution The output presented below is based upon a preliminary NHIS Public Use database. Your Public Use database may produce slightly different SUDAAN output. PROC DESCRIPT DATA = HIS.infile FILETYPE=SAS DESIGN = WR; NEST STRATUM PSU ; WEIGHT WTF; VAR LDR TDV_R HLT_FP ; SUBGROUP SEX AGE2; LEVELS 2 4; TABLES SEX AGE2; PRINT NSUM WSUM MEAN SEMEAN / WSUMFMT=F10.0 MEANFMT=F8.5 SEMEANFMT=F8.5 ; Method 1: partial output: S U D A A N Software for the Statistical Analysis of Correlated Data Copyright Research Triangle Institute April 1996 Release 7.00 Number of observations read : 102467 Weighted count :261889548 Number of observations skipped : 0 (WEIGHT variable nonpositive) Denominator degrees of freedom : 187 Research Triangle Institute The DESCRIPT Procedure by: Variable, SEX. ----------------------------------------------------------------------------- | Variable | | SEX | | | Total | 1 | 2 | ----------------------------------------------------------------------------- | LDR | Sample Size | 102467 | 48809 | 53658 | | | Weighted Size | 261889549 | 127570237 | 134319312 | | | Mean | 0.13797 | 0.18013 | 0.09793 | | | SE Mean | 0.00178 | 0.00250 | 0.00178 | ----------------------------------------------------------------------------- | TDV_R | Sample Size | 102467 | 48809 | 53658 | | | Weighted Size | 261889549 | 127570237 | 134319312 | | | Mean | 5.90759 | 4.90385 | 6.86089 | | | SE Mean | 0.09060 | 0.10039 | 0.12407 | ----------------------------------------------------------------------------- | HLT_FP | Sample Size | 101277 | 48266 | 53011 | | | Weighted Size | 258963568 | 126221708 | 132741859 | | | Mean | 0.10126 | 0.09124 | 0.11079 | | | SE Mean | 0.00157 | 0.00188 | 0.00176 | ----------------------------------------------------------------------------- Method 1: partial output: S U D A A N Software for the Statistical Analysis of Correlated Data Copyright Research Triangle Institute April 1996 Release 7.00 Number of observations read : 102467 Weighted count :261889548 Number of observations skipped : 0 (WEIGHT variable nonpositive) Denominator degrees of freedom : 187 Research Triangle Institute The DESCRIPT Procedure by: Variable, AGE2. ----------------------------------------------------------------------------- | Variable | | AGE2 | | | Total | 1 | 2 | ----------------------------------------------------------------------------- | LDR | Sample Size | 102467 | 29711 | 40801 | | | Weighted Size | 261889549 | 70670755 | 108040689 | | | Mean | 0.13797 | 0.08894 | 0.18489 | | | SE Mean | 0.00178 | 0.00269 | 0.00268 | ----------------------------------------------------------------------------- | TDV_R | Sample Size | 102467 | 29711 | 40801 | | | Weighted Size | 261889549 | 70670755 | 108040689 | | | Mean | 5.90759 | 4.29682 | 4.88589 | | | SE Mean | 0.09060 | 0.09797 | 0.12432 | ----------------------------------------------------------------------------- | HLT_FP | Sample Size | 101277 | 29183 | 40423 | | | Weighted Size | 258963568 | 69438212 | 107054300 | | | Mean | 0.10126 | 0.02552 | 0.06610 | | | SE Mean | 0.00157 | 0.00129 | 0.00168 | ----------------------------------------------------------------------------- ---------------------------------------------------------------- | Variable | | | | | | | 3 | 4 | ---------------------------------------------------------------- | LDR | Sample Size | 20000 | 11955 | | | Weighted Size | 51713265 | 31464840 | | | Mean | 0.14461 | 0.07606 | | | SE Mean | 0.00293 | 0.00251 | ---------------------------------------------------------------- | TDV_R | Sample Size | 20000 | 11955 | | | Weighted Size | 51713265 | 31464840 | | | Mean | 7.08504 | 11.09843 | | | SE Mean | 0.17859 | 0.30642 | ---------------------------------------------------------------- | | | | | | HLT_FP | Sample Size | 19834 | 11837 | | | Weighted Size | 51315866 | 31155190 | | | Mean | 0.16651 | 0.28344 | | | SE Mean | 0.00356 | 0.00519 | ---------------------------------------------------------------- Method 2 Partial Output S U D A A N Software for the Statistical Analysis of Correlated Data Copyright Research Triangle Institute April 1996 Release 7.00 Number of observations read : 102467 Weighted count :261889548 Number of observations skipped : 0 (WEIGHT variable nonpositive) Denominator degrees of freedom : 4030 Research Triangle Institute The DESCRIPT Procedure by: Variable, SEX. ----------------------------------------------------------------------------- | Variable | | SEX | | | Total | 1 | 2 | ----------------------------------------------------------------------------- | LDR | Sample Size | 102467 | 48809 | 53658 | | | Weighted Size | 261889549 | 127570237 | 134319312 | | | Mean | 0.13797 | 0.18013 | 0.09793 | | | SE Mean | 0.00174 | 0.00231 | 0.00184 | ----------------------------------------------------------------------------- | TDV_R | Sample Size | 102467 | 48809 | 53658 | | | Weighted Size | 261889549 | 127570237 | 134319312 | | | Mean | 5.90759 | 4.90385 | 6.86089 | | | SE Mean | 0.07704 | 0.08503 | 0.11403 | ----------------------------------------------------------------------------- | HLT_FP | Sample Size | 101277 | 48266 | 53011 | | | Weighted Size | 258963568 | 126221708 | 132741859 | | | Mean | 0.10126 | 0.09124 | 0.11079 | | | SE Mean | 0.00152 | 0.00174 | 0.00182 | ----------------------------------------------------------------------------- Method 2 Partial Output S U D A A N Software for the Statistical Analysis of Correlated Data Copyright Research Triangle Institute April 1996 Release 7.00 Number of observations read : 102467 Weighted count :261889548 Number of observations skipped : 0 (WEIGHT variable nonpositive) Denominator degrees of freedom : 4030 Research Triangle Institute The DESCRIPT Procedure by: Variable, AGE2. ----------------------------------------------------------------------------- | Variable | | AGE2 | | | Total | 1 | 2 | ----------------------------------------------------------------------------- | LDR | Sample Size | 102467 | 29711 | 40801 | | | Weighted Size | 261889549 | 70670755 | 108040689 | | | Mean | 0.13797 | 0.08894 | 0.18489 | | | SE Mean | 0.00174 | 0.00271 | 0.00254 | ----------------------------------------------------------------------------- | TDV_R | Sample Size | 102467 | 29711 | 40801 | | | Weighted Size | 261889549 | 70670755 | 108040689 | | | Mean | 5.90759 | 4.29682 | 4.88589 | | | SE Mean | 0.07704 | 0.09116 | 0.11805 | ----------------------------------------------------------------------------- | HLT_FP | Sample Size | 101277 | 29183 | 40423 | | | Weighted Size | 258963568 | 69438212 | 107054300 | | | Mean | 0.10126 | 0.02552 | 0.06610 | | | SE Mean | 0.00152 | 0.00118 | 0.00157 | ----------------------------------------------------------------------------- ---------------------------------------------------------------- | Variable | | | | | 3 | 4 | ---------------------------------------------------------------- | LDR | Sample Size | 20000 | 11955 | | | Weighted Size | 51713265 | 31464840 | | | Mean | 0.14461 | 0.07606 | | | SE Mean | 0.00303 | 0.00269 | ---------------------------------------------------------------- | TDV_R | Sample Size | 20000 | 11955 | | | Weighted Size | 51713265 | 31464840 | | | Mean | 7.08504 | 11.09843 | | | SE Mean | 0.16109 | 0.28387 | ---------------------------------------------------------------- | HLT_FP | Sample Size | 19834 | 11837 | | | Weighted Size | 51315866 | 31155190 | | | Mean | 0.16651 | 0.28344 | | | SE Mean | 0.00351 | 0.00501 | ---------------------------------------------------------------- Best NHIS design using Durbin probabilities (not available to the public) and weights adjusted by post-stratification ----------------------------------------------------------------------------- | Variable | | SEX | | | Total | 1 | 2 | ----------------------------------------------------------------------------- | LDR | Sample Size | 102467 | 48809 | 53658 | | | Weighted Size | 261889549 | 127570237 | 134319312 | | | Mean | 0.13784 | 0.17991 | 0.09789 | | | SE Mean | 0.00170 | 0.00221 | 0.00182 | ----------------------------------------------------------------------------- | TDV_R | Sample Size | 102467 | 48809 | 53658 | | | Weighted Size | 261889549 | 127570237 | 134319312 | | | Mean | 5.90468 | 4.89733 | 6.86141 | | | SE Mean | 0.07511 | 0.08320 | 0.11217 | ----------------------------------------------------------------------------- | HLT_FP | Sample Size | 101277 | 48266 | 53011 | | | Weighted Size | 258974266 | 126232939 | 132741328 | | | Mean | 0.10127 | 0.09125 | 0.11080 | | | SE Mean | 0.00137 | 0.00159 | 0.00165 | ----------------------------------------------------------------------------- Best NHIS design using Durbin probabilities (not available to the public) and weights adjusted by post-stratification Post-stratified estimates by: Variable, AGE2. ----------------------------------------------------------------------------- | Variable | | AGE2 | | | Total | 1 | 2 | ----------------------------------------------------------------------------- | LDR | Sample Size | 102467 | 29711 | 40801 | | | Weighted Size | 261889549 | 70670755 | 108040689 | | | Mean | 0.13784 | 0.08845 | 0.18484 | | | SE Mean | 0.00170 | 0.00258 | 0.00248 | ----------------------------------------------------------------------------- | TDV_R | Sample Size | 102467 | 29711 | 40801 | | | Weighted Size | 261889549 | 70670755 | 108040689 | | | Mean | 5.90468 | 4.29787 | 4.87876 | | | SE Mean | 0.07511 | 0.09066 | 0.11858 | ----------------------------------------------------------------------------- | HLT_FP | Sample Size | 101277 | 29183 | 40423 | | | Weighted Size | 258974266 | 69441900 | 107059972 | | | Mean | 0.10127 | 0.02555 | 0.06624 | | | SE Mean | 0.00137 | 0.00116 | 0.00153 | ----------------------------------------------------------------------------- ---------------------------------------------------------------- | Variable | | | | | 3 | 4 | ---------------------------------------------------------------- | LDR | Sample Size | 20000 | 11955 | | | Weighted Size | 51713265 | 31464840 | | | Mean | 0.14484 | 0.07587 | | | SE Mean | 0.00298 | 0.00268 | ---------------------------------------------------------------- | TDV_R | Sample Size | 20000 | 11955 | | | Weighted Size | 51713265 | 31464840 | | | Mean | 7.08472 | 11.09687 | | | SE Mean | 0.16180 | 0.27613 | ---------------------------------------------------------------- | HLT_FP | Sample Size | 19834 | 11837 | | | Weighted Size | 51315313 | 31157082 | | | Mean | 0.16633 | 0.28322 | | | SE Mean | 0.00342 | 0.00487 | ---------------------------------------------------------------- Remark on Examples A comparison of the three SUDAAN examples shows that Method 2 performs quite well when compared to the "best" internal NCHS variance design for the NHIS. Based on limited preliminary evidence, it appears that for means, Method 2 typically provides standard errors in close agreement with, while slightly larger than, the standard errors produced by the NCHS "best" method. Method 1 tends to provide slightly larger standard errors than Method 2 does, although the sample output does include examples where the Method 1 standard error is smaller than the Method 2 standard error. Reference: (1977) Cochran, W. G., Sampling techniques (3rd ed), John Wiley & Sons Notes for Year 2000 application (added 01/21/98) The variance estimation methods of this document may be applied to the Year 2000 Objectives Public Use File. The following changes must be made: The design information variables are all in the same file locations with the exception of "WTF". Substitute: WTF 207-212 'FINAL BASIC WEIGHT' The PSU check for method 2 should now read: As a check, the user should observe the following counts: Certainty Strata PSUs 3804 Non-certainty Strata PSUs 259 Total PSUs 4063 Notes on the 1996 NHIS (added 04/17/98) In 1996 the NHIS survey underwent a transition from a paper-and-pencil to a computer-assisted interview process. This transition resulted in roughly 5/8 of the available full sample being targeted for processing and public release. In 1997 the full sample was again implemented. For 1996 the reader should substitute the information on pages 3 and 4 and the top of page 5: Design Information Available on the NHIS Public Use Databases. Method 1 - 187 Strata containing 2 PSUs per stratum sampled with replacement Method 2 - Multiple PSUs per Stratum design sampled with replacement with the 1996 information on the following pages: Design Information Available on the 1996 NHIS Public Use Databases. The following variables are used to produce code for variance estimation. Field locations below are from the PERSON level database, but may change on other databases; the user should check the file documentation. Variable Name Location Field Label STRAT96* 354-357 'COLLAPSED VARIANCE STRATUM' PSU96* 358 'VARIANCE PSU' SUB_V 342-343 'SUBSTRATUM FOR VARIANCE ESTIMATION' SSU 344-350 'SECONDARY SAMPLING UNIT' PANEL 352 'PANEL 4' NSR96* 353 'NSR STATUS VARIABLE' WTF 219-227 'FINAL BASIC WEIGHT' (*indicates modified design variables added to the 1996 databases) Two methods of variance estimation are now provided. Method 1.96 -98 Strata containing 3 PSUs per stratum sampled with replacement Here, the NHIS universe has been partitioned into 98 collapsed strata with 3 PSUs per stratum. All PSUs are treated as sampled with replacement within their respective strata. This method will provide somewhat conservative standard errors, and this standard error estimator itself has less stability than the standard error estimator described by Method 2.96 below. Coding required, (SAS code provided): STRATUM = INT(STRAT96/10) * 10 ; PSU = PANEL ; Note, INT ( ) is the Integer-value SAS function, e.g., INT(2.3) = 2 As a check the user should observe 98*3 = 294 PSUs when using the full database. For the above simplification of the NHIS sample design structure, the following SUDAAN design statements may be used. (Note, the input file must first be sorted by STRATUM and PSU variables). PROC ... DESIGN = WR; NEST STRATUM PSU ; WEIGHT WTF; Method 2.96 - Multiple PSUs per Stratum design sampled with replacement This method provides for more statistically efficient variance estimation than Method 1.96, since it makes better use of the sampling design information. Its application is limited to software that can handle multiple PSUs per stratum, e.g., SUDAAN. For this method the original certainty PSUs are partitioned by aggregations of the original race-ethnic density strata used in sampling. The first randomly sampled unit is actually the SSU variable which is now treated as the PSU variable. (Note, a certainty PSU unit contributes nothing to the variance at the PSU sampling level). Non-certainty strata PSUs are treated as being sampled with replacement within their respective strata. Coding required (SAS code provided): IF NSR96 = 1 THEN DO; /*1996 certainty strata PSUs */ STRATUM = STRAT96*100 + SUB_V; PSU = SSU END; ELSE DO; /* 1996 non-certainty PSU */ STRATUM = STRAT96 ; PSU = PSU96 ; END; As a check, the user should observe the following counts: Certainty Strata PSUs 1736 Non-certainty Strata PSUs 240 Total PSUs 1976 For the Method 2.96 design structure, the following SUDAAN design statements may be used. (Note, the input file must first be sorted by STRATUM and PSU variables.) PROC ... DESIGN = WR; NEST STRATUM PSU ; WEIGHT WTF ; Caution. Both Method 1.96 and Method 2.96 should only be used on a full sample person database. Using this method with subsetted data may lead to incorrectly computed standard errors. (See the section Subsetted Data Analysis in the 1995 section). If using a subsetted data set, the user should check the degree of agreement in the PSU counts with the values presented above for either of the two methods. Unlike Method 1 for 1995, Method 1.96 is not robust for analyzing subsetted survey data. CAUTION A typically used rule-of-thumb for degrees of freedom to associate with a standard error is the quantity (number of PSUs - number of strata). This rule assumes that the PSUs are somewhat comparable in size. For Method 2.96 this rule may be grossly inaccurate since the concept of PSU is quite different for certainty and non-certainty strata. Certainty strata PSUs of Method 2.96 have small weighted values relative to those of non-certainty PSUs. The rule-of- thumb degrees of freedom for Method 1.96 is 196, and Method 2.96 should have a true degrees of freedom exceeding that of Method 1.96. However, for practical purposes, any degrees of freedom exceeding 120 can be treated as infinite, i.e., one uses a normal Z-statistic instead of a t-statistic for testing. Note, that a one-tailed critical t0.025 at 120 degrees of freedom is 1.98 while at an infinite degrees of freedom (i.e., a z-value) is 1.96. If a variable of interest covers most of the NHIS PSUs, the limiting value would probably be adequate for analysis. The user should consult a mathematical statistican for discussion of degrees of freedom. The observant reader may notice that the 1996 method 1.96 has a larger rule of thumb degrees of freedom than the corresponding 1995 method 1. The 1996 variance estimation design consists of collapsed strata that may introduce a much larger stratum-collapse bias than occurred in 1995, and furthermore, the PSUs within each 1996 collapsed stratum have greater PSU weight diversity than in 1995 which may reduce stability. The section on SUBSETTED DATA ANALYSES in the 1995 section should be read considering the changes provided in this 1996 section.
