the PPD score provides information regarding the individuals’ perceptions of the relative proportion of their peers who have engaged in a variety of delinquent behaviors. A total PPD score was derived by multiplying the mean score of the individual items by the number of items, resulting in a maximum possible score of 65. This method ensures that the total peer scores for participants with missing item scores are not artificially reduced. Participants who responded to less than 60% of the individual peer items (8 items) were dropped from our analyses (132 individuals), as the mean from such few responses is unreliable (Elliott et al., 1989). The PPD measure was only included in our questionnaire after January 10, 1998; participants tested prior to this date did not have responses for the PPD measure. Consequently, a further 173 participants were excluded. Five participants were excluded because they claimed not to have any friends, and so were not questioned further on this subject.
