Missing data are a pervasive problem in many psychological applications in the real world. In this article we study the impact of dropout on the operational characteristics of several approaches that can be easily implemented with commercially available software. These approaches include the covariance pattern model based on an unstructured…

Methods for modeling transitions between health-risk states over time when multiple indicators of health risk are available are discussed, and a latent transition model is presented as an alternative to approaches that analyze indicators separately or use summative indices. The approach is illustrated through a self-report study of…

There is evidence to suggest that the effects of behavioral interventions may be limited to specific types of individuals, but methods for evaluating such outcomes have not been fully developed. This study proposes the use of finite mixture models to evaluate whether interventions, and, specifically, group randomized trials, impact participants…

A model for multilevel ordinal response data is described that allows for nonproportional odds for a subset of explanatory variables. The model, the multilevel thresholds of change model, focuses on modeling the K-1 thresholds that delineate membership in the "K" ordered stages. The model is illustrated with data from a cancer prevention study.…

Describes the use of multilevel models (MLMs) for studies in which individuals are randomized by groups to treatment condition. Uses data from the Safer Choices study, an evaluation of a theory-based multi-component program to prevent sexually transmitted diseases and pregnancy, to illustrate the application of MLMs for both continuous and…

Longitudinal data from a school-based alcohol-prevention trial involving 385 girls and 353 boys were used to show how a model using individual growth modeling and a covariance structure approach can investigate relationships among individual changes in two domains (positive and negative alcohol expectancies). Advantages of the approach are…

Describes the application of multilevel statistical models to the evaluation of a multi-site community-based intervention and explicates key issues in the design,analysis, and presentation of results. The initiative described, "Fighting Back, is designed to reduce the demand for illegal drugs and alcohol in a community. (SLD)