IBM® SPSS® Amos™ 28

This plugin draws a simple growth curve model with "intercept" and "slope" latent variables. The plugin automatically constrains parameters in a way that is appropriate for many growth curve models. The following parameter constraints are imposed.

▪The regression weights for the "intercept" latent variable are fixed at 1.

▪The regression weights for the "slope" latent variable are fixed at equally spaced intervals starting at 0 and ending at 1. For example, if measurements were made at 5 time points, the 5 regression weights are fixed at 0, 0.25, 0.50, 0.75 and 1.00.

▪The intercepts of the measured variables are fixed at zero.

▪The error variances are constrained to be equal by giving each error variance the same name, Var.

▪The error variables are required to be uncorrelated.

▪The means and variances of the "intercept" and "slope" latent variables are unconstrained.

▪The covariance between "intercept" and "slope" is unconstrained.

You can modify the parameter constraints after Amos draws the path diagram for the growth curve model. For example, you will want to change the regression weights for the "slope" latent variable if your time points are not equally spaced. If you want to remove the equality constraints on the error variances you can do so by deleting the parameter name, Var, which is automatically assigned to all of the error variances.

To use the growth curve plugin, click Plugins→Growth Curve Model.