The general purpose of weighting is to scale up the sample estimates to represent the target survey population. For SASS, a base weight (e.g., the inverse of the sampled teacher's probability of selection) is used as the starting point. Next, a series of nonresponse adjustment factors are calculated and applied using information from the 2003–04 SASS nonresponse bias analysis and information about the respondents known from the sampling frame data. Finally, for some files, a ratio adjustment factor is calculated and applied to the sample to adjust the sample totals to the frame totals. The product of these factors is the final weight for each SASS respondent, which appears as DFNLWT on the SASS Public School District data file, AFNLWGT on all SASS Principal data files, SFNLWGT on all SASS School data files, TFNLWGT on all SASS Teacher data files, and MFNLWGT on all SASS Library Media Center data files.
The counts in table 1 do not necessarily match the frame counts because some cases in the frame were found to be ineligible (i.e., out-of-scope) and because not all data files (e.g., principal or library media center) are post-stratified to match the frame counts.