Latent Growth Modeling: Orthogonal Polynomial vs. Raw Time Coding

[ahmad]

Hi,

I have a question regarding the interpretation of latent growth factors in a standard linear growth model (with raw time coding) versus an orthogonal polynomial growth model.

I understand that in the standard linear model, the intercept typically represents the expected value at the initial time point (when time is coded starting at zero). In contrast, in orthogonal polynomial models, the intercept represents the overall mean across time points.

However, I am less clear about the interpretation of the linear slope in these two approaches. What is the conceptual difference between the linear slope in the standard linear growth model and the linear component in an orthogonal polynomial model?

I would greatly appreciate your time and help.

Best,

A