The six metropolitan areas were New York, Washington, D.C., Miami, Chicago, Denver, and Los Angeles. Persons age 18-34 identified as current cigarette smokers by the household screening respondents were also oversampled. Although they are not oversampled, the survey does include persons living in noninstitutional group quarters when these units fall into the sample. This primarily consists of students living in dormitories, but also includes some homeless persons who are living in shelters at the time that the shelter addresses are selected. Introductory letters are sent to sampled addresses, followed by an interviewer visit.
Interviewers attempt to conduct interviews in a private place, away from other household members.
After these answer sheets are completed, they are placed by the respondent in an envelope, which is sealed and mailed to the contractor, Research Triangle Institute, with no personal identifying information attached. Upon receipt, questionnaires are checked for critical identification and demographic data, then keyed to disk. This creates a file consisting of one record for each completed interview. Extensive within-record consistency checks and resolution of most inconsistencies and missing data are done using machine editing routines, called logical imputation. For some key variables that still have missing values after the application of logical imputation, statistical imputation is used to replace the missing data with appropriate valid response codes.