A Stata Plugin for Estimating Group-Based Trajectory ...

A Stata Plugin for Estimating Group-Based Trajectory Models Bobby L. Jones University of Pittsburgh Medical Center Daniel S. Nagin Carnegie Mellon University May 21, 2012 This work was generously supported by National Science Foundation Grants SES-102459 and SES-0647576 Abstract Group-Based Trajectory models are used to investigate population differences in the developmental courses of behaviors or outcomes . This article demonstrates a new Stata command, traj, for fitting to longitudinal data finite (discrete) mixture models designed to identify clusters of individuals following similar progressions of some behavior or outcome over age or time. Censored normal, Poisson, zero-inflated Poisson, and Bernoulli distributions are supported. Applications to psychometric scale data, count data, and a dichotomous prevalence measure are illustrated. Introduction A developmental Trajectory measures the course of an outcome over age or time.

Mar 29, 2013 · the sequential realizations of the elements of Y i , y it ... model( string) probability distribution for the dependent variables (required). Models supported: ... polynomial type (0=intercept, 1=linear, 2=quadratic, 3=cubic) for each group trajectory (required). min( real) minimum value for the censored normal model (required for cnorm).

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  Model, Stata, Sequential, Intercepts

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