The PROSPER project is an evidence-based intervention program with longitudinal data on 28 communities in Iowa and Pennsylvania randomized into 14 control and 14 intervention units (for more information on intervention design see Spoth et al., 2013; Spoth, Redmond, et al., 2007). Students completed in-school questionnaires in the fall and spring of 6th grade with annual spring follow-ups until the 12th grade. See Figure 1 for the PROSPER CONSORT diagram (for design details see Spoth et al, 2013). In-school questionnaire included a request for participants to nominate up to two best friends and five additional close friends in their grade and school who also participated in the PROSPER project. Additionally, a random sample of 2,267 families of youth in Cohort 2 of the PROSPER project were invited to participate in the in-home data collections, which consisted of interviews and parent and adolescent questionnaires in Waves 1 through 5; 979 (43%) participated.
