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Epidemiology Surveys

Dropped Variables

Processors dropped many variables in the NCS-R, NLAAS, and NSAL source datasets, for the following reasons:

  1. To protect the identity of research subjects, including dropping source variables for constructed demographics created to mask identity;

  2. If they were source variables for constructed variables created for other purposes (e.g., NSAL's variable E14a-e15a, which has combined data from three questions that resulted from routing respondents through three different question wordings to gather the same data); or

  3. If they were the following types of computer-assisted instrument variables (the figure below shows examples of how these would appear in the NCS-R, NLAAS, and NSAL interactive codebooks):

    • Open-ended question with text response;

    • Open-ended "other specify" question with text response;

    • Instrument screen with introductory text ("ENTER 1 TO CONTINUE");

    • Interviewer checkpoint or instruction screen; or

    • Interviewing software routing check.

More information on dropped variables (including a list of the variables) can be found on pages 44-77 of the Data Processing Notes.