Within each PSU, area segments were selected with probability proportional to a composite size measure that was designed to overrepresent concentrated Hispanic and black neighborhoods, as well as younger individuals.3 Dwelling units were selected from each sample segment. The target population included all 12-year-old or older civilian residents of households (including civilians residing on military installations) and noninstitutional group quarters (e.g., college dormitories, homeless shelters, rooming houses). Persons excluded from this target population included military personnel on active duty, transient populations (such as homeless people who do not reside in shelters), and residents of institutional group quarters (e.g., jails, hospitals). Data collection was continuous over the 1998 calendar year.
Survey data were collected through personal visits to each selected residence. Introductory letters were mailed to each residence and were used to explain the survey prior to the interviewer's visit. Upon arrival, the NHSDA field representative conducted a short voluntary screening procedure with any resident of the household 18 years old or older who was capable of providing information on the age, race/ethnicity, gender, and marital status of each resident 12 years old or older. This information was used in a random selection procedure to determine whether any resident members were eligible for an in-depth interview (either one, two, or no individuals were selected). The interviewer had no control over this selection procedure. The 1998 within-household person selection probabilities were based on the race/ethnicity of the head of household and the ages of each household member. Selected individuals then were asked if they would complete a voluntary interview. NHSDA field representatives conducted the interviews using a paper-and-pencil questionnaire that included both interviewer-administered questions and self-administered answer sheets (for collection of sensitive information). All screening and interview responses were kept confidential.
In 1998, a total of 33,128 eligible dwelling unit members were selected for an interview; of these, a total of 25,500 interviews were completed (4,903 interviews were conducted in California, 3,869 interviews were conducted in Arizona and 16,728 interviews were conducted in the remaining States). Total response rates for screening and interviewing were 93.0% and 77.0%, respectively.
This page was last updated on June 03, 2008.