Abstract
The effect of an independent variable on random slopes in growth modeling with latent variables is conventionally used to examine predictors of change over the course of a study. This article demonstrates that the same effect of a covariate on growth can be obtained by using final status centering for parameterization and regressing the random intercepts (or the intercept factor scores) on both the independent variable and a baseline covariate–the framework used to study change with classical regression analysis. Examples are provided that illustrate the application of an intercept-focused approach to obtain effect sizes–the unstandardized regression coefficient, the standardized regression coefficient, squared semi-partial correlation, and Cohen’s f2–that estimate the same parameters as respective effect sizes from a classical regression analysis. Moreover, statistical power to detect the effect of the predictor on growth was greater when using random intercepts than the conventionally used random slopes.
Acknowledgements
I would like to thank Mike Stoolmiller for writing the R program that generates parameters for effect sizes used in the Monte Carlo study and for assistance with the Mplus programming for the illustrative and Monte Carlo analyses.