created by summing responses (α = .66 at baseline). High scores indicate higher levels of social desirability. Mandated students may be more motivated to underreport alcohol use levels than volunteer students. Previously we reported from a different sample that mandated students with high demand characteristics tended to report lower levels of alcohol and drug use (White et al., 2008). Therefore, although there was no difference in social desirability between two PFI conditions at baseline with the present sample (White et al., 2007), we controlled for social desirability mean levels (and variances) by constraining them to be equal across classes in mixture analysis.6
