Attrition comparisons have revealed few differences between dropouts and completers; however, more highly educated parents were more likely to stay in the study than less highly educated parents (Spoth, Redmond, & Shin, 1998). All study procedures, including parent consent and adolescent assent protocols, which have been described in detail elsewhere (Spoth et al., 2009), were approved by the Human Subjects Review committees at Iowa State University and the University of Washington.
