The software program Mplus Version 5 (Muthén and Muthén, 1998–2007) was used to estimate all latent class and transition models. For the current study, the analyses proceeded in several stages. First, measurement models of drinking-outcome indicators were estimated at each time point for each treatment arm. Second, cross-sectional patterns of drinking classes and response frequencies for each drinking-outcome indicator were evaluated for each treatment arm. Third, several latent transition models were estimated to test the assumption of invariant transition probabilities across treatment arms. Fourth, latent transition models were estimated to examine the effect of treatment assignment on drinking classes and transition probabilities across time. Finally, a model that incorporated alcohol dependence as a time-invariant covariate predicting drinking-class membership and transitions between drinking classes was estimated. Using the results from this final model and each individual’s most likely class membership, the mean number of alcohol-dependence symptoms across classes was estimated to evaluate the clinical relevance of the results. It is important to note that these “model estimated means” are based on posterior probabilities of class membership and are estimated in the model solution.
