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. Author manuscript; available in PMC: 2010 Aug 1.
Published in final edited form as: Drug Alcohol Depend. 2009 May 14;103(3):99–106. doi: 10.1016/j.drugalcdep.2008.12.019

Table 2.

Growth Mixture Model: Optimization of Trajectory Number

Model Latent Classes Covariates Free parameters Loglikelihood BIC Entropy BLRT (parameter difference), p - value
1 2 No 8 -2926.37 5908.52 .90 1122.09(3), p <.0001
2 3 No 11 -2844.65 5766.01 .78 163.440(3), p <.0001
3 4 No 14 -2817.08 5731.79 .73 55.137(3), p <.0001
4 5 No 17 -2802.60 5723.75 .76 28.96(3), p =.0312
5 6 No 20 -2790.85 5721.17 .77 23508(3), p =.19
6 4 Yes 50 -2230.96 4802.54 .78 267.98 (19), p =.67
7 3 Yes 35 -2276.35 4791.14 .77 213.18 (15), p <.0001

Note. BIC, Bayesian information criterion (-2logL + r ln n), where L is the model’s maximum likelihood value, n is the sample size, and r is the number of free model parameters; BLRT, Bootstrap Likelihood Ratio Test for k (H0) versus k-1 classes; Entropy (EK=1-(piklog(pik))/nlog(K)), where pik is the conditional probability of individual i in class K, is a measure of classification quality, with values closer to one representing better classification.