# Growth modeling within a multilevel modeling framework

In an earlier episode of Office Hours, Patrick addressed the question, “What is growth curve modeling?” In this episode he explores how a growth curve model can be estimated within the multilevel linear modeling (MLM) framework. Patrick begins by reviewing the assumption of independence in the general linear model and how this is violated when data are nested (e.g., children nested within classrooms). He then describes how the MLM allows for the direct modeling of nested data, and how this framework can be extended to estimate growth models in which repeated measures are nested within individual. He examines the unconditional growth model, the incorporation of time-invariant and time-varying covariates, and how the MLM growth model can be expanded to include additional levels of nesting.

To see all episodes in this series, see our Growth Modeling
playlist.

## My advisor told me I should group-mean center my predictors in my multilevel model because it might “make my effects significant” but this doesn’t seem right to me. What exactly is involved in centering predictors within the multilevel model?

How to specify multilevel models to obtain within- and between-group effects through centering lower-level predictors.

## I fit a multilevel model and got the warning message “G Matrix is Non-Positive Definite.” What does this mean and what should I do about it?

Received the cryptic warning message “G matrix is non-positive definite”? Learn what this means and what to do about it.

## What is the difference between a growth model estimated as a multilevel model versus as a structural equation model?

This very common question reflects a great deal of unnecessary confusion about how to select a specific analytic approach for modeling longitudinal data. The general…

## What’s the best way to determine the number of latent classes in a finite mixture analysis?

Selecting the number of classes (or components) is one of the most challenging decisions to make when fitting a finite mixture model (including latent class analysis and latent profile analysis). In this post, we talk through the conventional wisdom on class enumeration, as well as when this breaks down.

## How can I define nonlinear trajectories in a growth curve model?

Growth curve models, whether estimated as a multilevel model (MLM) or a structural equation model (SEM), have become widely used in many areas of behavioral,…