In addition to the sibling pairs sample, supplemental samples were also drawn based on ethnicity (Cuban, Puerto Rican, and Chinese) and physical disability. Add Health also oversampled African American adolescents with highly educated parents to provide sufficient cell sizes for analyses broken down by race and socioeconomic status. Finally, a special ‘saturated’ sample was included in Wave I by selecting all enrolled students from two large schools and 14 small schools for in-home interviews. Complete social network data were collected in the saturated field-settings by generating a large number of romantic and friendship pairs for which both members of the pair had in-home interviews. These data provide unbiased and complete coverage of the social networks and romantic partnerships in which adolescents are embedded. A parent, usually the resident mother, also completed a 30-minute interviewer-assisted interview at Wave I. The core sample plus the special samples produced a sample size of 20,745 adolescents interviewed in the home at Wave I with a response rate of 78.9%. The Wave I in-home sample represents the national cohort that is followed prospectively through time, and thus this innovative design remains a major strength of the longitudinal data as well.
