They were reinterviewed between April and August 1996. In addition to its longitudinal selleck chemicals Belinostat design, another key element of Add Health is its social network design in which 16 schools were ��saturated�� (all students in the schools were interviewed) and all respondents were asked to select up to 10 friends. Friends who were members of the same school were identified from a school roster. Respondents completed this friendship nomination process in two follow-up, in-home interviews. The data collection design allows researchers to match individuals in the Add Health study to investigate peer influences on behavior based on direct reports of friends�� behaviors. This study continues to be the best and largest source of network and behavior data for investigation of influence and selection processes.

In this study, we focus on the two largest ��saturated�� schools. The remaining saturated schools were small and saturated as a result of sampling constraints, not by design, and not large enough to be amenable to our modeling approach. For ease of discussion we differentiate these schools based on the prevalence of current smoking in the student body: one has a low prevalence, and the other a high prevalence. These analyses focus exclusively on students entering 10th and 11th grades at Wave I of the data collection. We excluded 12th graders because they were not interviewed at Wave II, and excluded 7�C9th graders because of the low prevalence and lower likelihood of current smoking. This led to a sample of 419 students in the school with a high prevalence of smoking, and a sample of 1193 in the school with a low prevalence of smoking.

Measures For this study we incorporated important demographic variables: grade, gender, race/ethnicity, and parental education as reported in their in-home survey responses. Grade is coded as the specific grade level each student was in at Wave I. Gender is coded as male or female. Race/ethnicity was categorical, based on survey responses. Parental education is based on the highest level of education attained by either parent (parent report) and is coded as 1 = less than high school, 2 = graduate of high school, 3 = some college or trade school, and 4 = graduate of college or university. Friendship nominations were obtained by asking participants to nominate their five best male and five best female friends.

Nominations of students outside of the school were dropped because these students were not consented into the study and therefore were not included in any survey activities. We also flagged students who were, by design, only allowed to nominate one friend (approximately 5% of Entinostat the sample) and controlled for this in our models. We investigate changes in smoking behavior based on two variables derived from measures collected at Wave I and Wave II. ��Current smoking status�� is coded as a dichotomous variable marking any past-month smoking reported at Wave I and Wave II.