AIDS KNOWLEDGE AND ATTITUDES SUPPLEMENT NOTES This data file contains the part of the 1991 National Health Interview Survey related to AIDS Knowledge and Attitudes. For this survey, information was collected from one randomly selected adult (18 years and older) from each family who participated in the NHIS. The AIDS survey covered several different topic areas: 1. Sources of Information 2. Knowledge-included true-false items on modes of transmission and pathogenesis; respondents were also asked to rate the likelihood of transmission of the AIDS virus by various forms of casual contact 3. Experience with blood donation 4. Experience with HIV antibody testing 5. Awareness of AZT 6. Perceptions of the effectiveness of condoms and knowledge about condom use 7. Perceived risk of acquiring HIV infection The response rate to the AIDS survey was 86 percent and was calculated as follows: The response rate to the NHIS Core questionnaire was 96 percent. Of the eligible sample persons from the CORE, 90 percent responded to the AIDS questionnaire. Multiplying these two response rates together yields the overall response rate to the AIDS section (86 percent). Each record included in this AIDS data file contains a final weight (data locations 207-212). Weights must be used to make accurate estimates based on this data file. Because the AIDS survey included only one adult per NHIS family, the weight on this file is different from the weight for the same adult on the NHIS Core Person data file. Most of the weights for records in the AIDS data file are between 2000 and 8000. However, due to the design of the NHIS and the weighting procedure, there are some records with very large weights (> 20,000). Analyses involving fairly small sample numbers may be heavily impacted by the inclusion of records with extremely large weights. Analysts are encouraged to look at the distribution of weights for records being analyzed to decide how to handle these weighting outliers. - 1 - Notes on Weighting: 1991 AIDS Public Use Data Documentation The final case weight in data locs. 201-206 produces national estimates based on the full 52 weeks of data included in the 1991 AIDS Knowledge and Attitudes data. The estimator embodied in the final case weight includes a ratio- adjustment to benchmark population estimates by age, sex, and race. This adjustment also attempts to reduce bias resulting from nonresponse and household noncoverage. The final case weight must be adjusted if the data user intends to develop estimates for shorter time periods, e.g., to analyze data for specific calendar months. The data contained in this data file will not provide reliable estimates for time periods of less than 4 weeks. To develop estimates for subsets of the 1991 AIDS data file, e.g., for specific calendar months, the file user must first identify cases by date of interview. This can be done be selecting on two fields the processing quarter (data loc. 5) and the processing week code (data locs. 19-20), which is numbered from 01 to 13 within each quarter. The table below shows how the quarter and processing week codes correspond to actual interview weeks. For example, to calculate estimates of AIDS knowledge for November 1990, the user would select only those cases where processing quarter = 4 and where processing week code = 04-08. Processing Processing Interview Quarter Week Week 1 01 Week 01 cancelled 1 02 Jan. 14 - Jan. 20 1 03 21 - 27 1 04 28 - Feb. 3 1 05 Feb. 4 - 10 1 06 11 - 17 1 07 18 - 24 1 08 25 - Mar. 3 1 09 Mar. 4 - 10 1 10 11 - 17 1 11 18 - 24 1 12 25 - 31 1 13 Apr. 1 - Apr. 7 2 01 8 - 14 2 02 15 - 21 2 03 22 - 28 2 04 29 - May 5 2 05 May 6 - 12 2 06 13 - 19 2 07 20 - 26 2 08 27 - June 2 2 09 June 3 - 9 2 10 10 - 16 2 11 17 - 23 2 12 24 - 30 - 2 - Processing Processing Interview Quarter Week Week 2 13 July 1 - July 7 3 01 8 - 14 3 02 15 - 21 3 03 22 - 28 3 04 29 - Aug. 4 3 05 Aug. 5 - 11 3 06 12 - 18 3 07 19 - 25 3 08 26 - Sept. 1 3 09 Sept. 2 - 8 3 10 9 - 15 3 11 16 - 22 3 12 23 - 29 3 13 30 - Oct. 6 4 01 Oct. 7 - 13 4 02 14 - 20 4 03 21 - 27 4 04 28 - Nov. 3 4 05 Nov. 4 - 10 4 06 11 - 17 4 07 18 - 24 4 08 25 - Dec. 1 4 09 Dec. 2 - 8 4 10 9 - 14 4 11 16 - 22 4 12 23 - 29 4 13 30 - Jan. 5 Final weights for subsets of the 1991 AIDS Knowledge and Attitudes data file, such as for a single month of data, may be calculated by multiplying the final case weight in data locs: 201-206 by 52/n, where n is the number of weeks of data in the subset being examined. The resulting adjusted final case weight will be approximate since it does not directly incorporate the age/race/sex poststratification adjustment described earlier. These weights for an n-week period may not yield estimates consistent with the benchmark population estimates by age, sex, and race. Data users who wish to develop more accurate estimates for subsets of the data, e.g., for specific months, can customize their own age/sex/race poststratification procedures if desired: 1) Create a temporary adjusted final case weight by multiplying the interim case weight (data locs. 172-177) by 52/n. 2) Determine age/sex/race poststrata appropriate to the intended analysis, making sure that each poststratum (e.g., black men aged 18-29) contains at least 50 cases. - 3 - 3) Sum the temporary adjusted case weights (i.e., the interim weights times 52/n) within each poststratum and divide the benchmark population in the poststratum, e.g., a Census count or estimate, by this sum. The result of this division is the age/sex/race poststratification adjustment factor. 4) Multiply the temporary adjusted case weight by the appropriate age/sex/race postratification factor to obtain final adjusted case weight. - 4 -