1974 National Study-A sample of 16,181 adolescents in
grades seven through twelve in the 48 contiguous states and
the District of Columbia was drawn using a two-stage
stratified random sampling design. Homerooms of students
stratified by grade level (7-8, 9-10, 11-12) were drawn in
each of 50 counties selected from strata varying in census
region, county population size, and ethnic status. In this
design, counties with more than 10 per cent Spanish-speaking
people, Native Americans, or Asian Americans were
oversampled. A total of 13,122 (81 per cent) adolescents in
643 homerooms (90 per cent of those sampled, or their
replacements) completed questionnaires, yielding an overall
response rate of 73 per cent.30