The covariance between level and shape in the latent growth curve model with estimated basis vector coefficients

Abstract

A LISREL representation of the Latent Growth Curve Model is used to generate the set of equations for the expectation of the vector of means and the covariance matrix in terms of the unknown population parameters. A dependency between the covariance of the level and shape parameters and the scalings of the shape basis vector is shown. A simulation is presented based on data presented by McArdle and Hamagami (1991) to show how the covariance changes as the basis vector coefficients are rescaled. The relationship is explained in terms of the algebraic solution to a system of equations. Keywords: Latent growth curves, structural equation modeling, LISREL.