Unrestricted Mixture Models for Class Identification in Growth Mixture Modeling

Growth mixture modeling has gained much attention in applied and methodological social science research recently, but the selection of the number of latent classes for such models remains a challenging issue, especially when the assumption of proper model specification is violated. The current simulation study compared the performance of a linear growth mixture model (GMM) for determining the correct number of latent classes against a completely unrestricted multivariate normal mixture model. Results revealed that model convergence is a serious problem that has been underestimated by previous GMM studies. Based on two ways of dealing with model nonconvergence, the performance of the two types of mixture models and a number of model fit indices in class identification are examined and discussed. This article provides suggestions to practitioners who want to use GMM for their research.