چکیده : 

This paper proposes growth mixture modeling to assess intervention effects in longitudinal randomized

trials. Growth mixture modeling represents unobserved heterogeneity among the subjects using a finitemixture

random effects model. The methodology allows one to examine the impact of an intervention

on subgroups characterized by different types of growth trajectories. Such modeling is informative

when examining effects on populations that contain individuals who have normative growth as well as

non-normative growth. The analysis identifies subgroup membership and allows theory-based modeling

of intervention effects in the different subgroups. An example is presented concerning a randomized

intervention in Baltimore public schools aimed at reducing aggressive classroom behavior, where only

students who were initially more aggressive showed benefits from the intervention