Turning to the selection and exposure effects of primary interest, Table 3 shows that students tend to select friends based on having the same alcohol onset status (drinker or nondrinker), net of covariates (t(11) = 8.5, p < .001) (H1). This effect did not vary across schools, as shown by the nonsignificant estimated standard deviation. Additional details can be obtained by constructing an ego–alter selection table (Table 4), showing the model-predicted propensities to select alters with the same or different drinking onset status, given ego’s drinking onset status (Ripley et al., 2012, Section 13.3). The log-odds ratio for choosing as a friend a particular person with the same onset status as oneself, compared to another person with a different onset status, assuming both have identical attributes as well as network embeddedness, is 0.039 – (–0.012) = 0.51 for nonusers, whereas it is 0.025 – (–0.060) = 0.85 for users. Thus, users are more selective in choosing friends based on same drinking status.
