The sample design of the survey has changed over time, but it has always been representative of the U.S. general population age 12 and older and has always oversampled youths and young adults. The 1995 NHSDA employed a multistage area probability sample of 17,747 persons. The first stage of selection is a sample of 115 Primary Sampling Units (PSUs), each consisting of counties (administrative subdivisions of States) or groups of counties such as metropolitan areas. Within these PSUs, segments (such as city blocks or enumeration districts) are selected. In 1995, 1,940 segments were selected, and in each of these segments a listing of all addresses was made, from which a sample of 66,431 addresses was selected. Of these, 56,469 were determined to be eligible sample units. In these sample units (which can be either households or units within group quarters), sample persons were randomly selected (with unequal probabilities) using a screening procedure carried out by interviewers.
The 1995 NHSDA sampled segments were allocated equally into four separate samples, one for each three month period during the year, so that the survey is essentially continuously in the field. By assigning the appropriate selection probabilities at the PSU, segment, and person levels, oversampling of certain subpopulations of interest is accomplished. In 1995, these subpopulations were young people (age 12-34), African-Americans and Hispanics. Persons age 18-34 identified as current cigarette smokers by the household screening respondents were also oversampled.
This page was last updated on June 16, 2008.