A SAS macro for estimating and visualizing individual growth curves
Longitudinal data analyses can be usefully supplemented by the plotting of individual growth curves. Unfortunately, such graphics can be challenging and tedious to produce. This article presents and demonstrates a SAS macro designed to automate this task. The OLStraj macro graphically depicts ordinary least squares (OLS)-estimated individual trajectories, describes interindividual variability in OLS-estimated growth parameters, and identifies possible outlier observations. Analytical developments are briefly outlined, and the use of the macro is demonstrated, with particular attention paid to the potential utility of the macro as both a data screening and post hoc diagnostic device. Potential limitations of the macro and suggestions for future developments are discussed. It is hoped that the program will be of use to applied researchers who seek to maximize the effectiveness of growth curve models in answering questions about stability and change.
Carrig, MM; Wirth, RJ; Curran, PJ
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