Families on TANF in Illinois: Employment Assets and Liabilities. Data Weighting Procedure

06/10/2003

We computed weights for the survey respondents using three factors, as summarized in Table A.3 and discussed below. The product of these three factors for a given survey respondent is the final sampling weight for that case.

Component 1: Sample Weight

The sample weight for each case in the survey sample accounts for the number of cases it represents in the sampling frame, based on the sample selection procedure. As indicated earlier, we designed a stratified sample in which the theoretical sampling rate was constant across the two strata, Cook County and downstate. Because we had to select whole cases, we actually sampled Cook County cases at a very slightly higher rate than downstate cases. The sample weight is the inverse of the actual probability of selection. For sampled cases in Cook County and downstate, respectively, its value is 62.93 and 63.09.

Table A.3
Components of the Survey Weights
Component Number Component Name and Purpose
1 Sample Weight

This component of the survey weights is the inverse of the probability of selection of a case into the survey sample from the sampling frame. It is computed separately for Cook County and the combined downstate counties.

2 Survey Response Adjustment

This component is the inverse of the survey response rate in Cook County and downstate. It adjusts the sample weight among the survey respondents to account for the difference in the survey response rate between Cook County and the downstate counties.

3 Post-Stratification Adjustment

This component is the ratio of cases in the sampling frame to weighted survey respondents (based on the product of factors 1 and 2) in five cells defined by geographic location, age of the grantee, and whether the TANF benefit in the sample month was positive or zero. Within each cell, it adjusts the weighted number of respondents so that it equals the sampling frame count.

Component 2: Survey Response Adjustment

This component compensates for the reduction in the sample due to cases that could not be interviewed for the reasons given in Table A.1. It is the inverse of the survey response rate. Because the response rate was slightly lower in Cook County than downstate, the value of this component is slightly higher in Cook County (1.28) than downstate (1.25).

Component 3: Post-Stratification Adjustment

This component of the survey weights is based on a post-stratification of the survey respondents into five cells as shown in Table A.4. This factor causes the sum of the weighted survey respondents to equal the number of cases in the sampling frame in each cell. The five cells were defined by three variables that were extracted from the Illinois DHS administrative data system in November 2001: residence in Cook County or downstate, the grantee's age less than or equal to 28 years or greater than 28 years, and a zero or positive TANF benefit amount. While in principle, these variables could be used to define eight cells, the infrequency of zero-benefit cases led us to consolidate them in a single cell. The values of the post-stratification adjustment factor range from 0.86 to 1.25. In general, the larger values are for cells containing cases with older grantees, which had a lower survey response rate than cases with younger grantees.

Table A.4
Post-Stratification Adjustment
  Zero TANF Benefit Positive TANF Benefit
Cook County Downstate
28 Years Old >28 Years Old 28 Years Old >28 Years Old
Number of Survey Respondents 30 184 129 48 25
Weighted Number of Survey Respondents 2,406 14,859 10,417 3,776 1,967
Number of Cases in Sampling Frame 2,859 12,728 12,074 3,378 2,456
Adjustment Factor 1.19 0.86 1.16 0.89 1.25

Final Survey Weights

The final weights for the survey respondents are the product of the three components discussed above. There is a unique weight for each of six cells, ranging in value from 69.17 to 98.24.(5)

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