What is a suppressor variable, and how does this differ from confounding and mediation?
A constant source of confusion within the multiple regression model (and the general linear model more broadly) relates to the terms suppression and s…
Category: Help Desk
What are ROC curves and how are these used to aid decision making?
ROC curves are used to identify cut points on continuous measures at which to make binary decisions. An example is a depression screener used to ident…
What exactly qualifies as intensive longitudinal data and why am I not able to use more traditional growth models to study stability and change over time?
This post considers the unique features of intensive longitudinal data (ILD) relative to other more traditional data structures and how we can appropr…
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…
My advisor told me to use principal components analysis to examine the structure of my items and compute scale scores, but I was taught not to use it because it is not a “true” factor analysis. Help!
We explain the difference between principal components analysis and exploratory factor analysis
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.
I’m reporting within- and between-group effects in from a multilevel model, and my reviewer says I need to address “sampling error” in the group means. What does this mean, and what can I do to address this?
Why between-group effects estimating in MLMs are sometimes biased, and what to do about it
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.
A reviewer recently asked me to comment on the issue of equivalent models in my structural equation model. What is the difference between alternative models and equivalent models within an SEM?
An equivalent model can be thought of as a re-parameterization of the original model. In other words, it is just a different way of “packaging” th…
I have a fair amount of missing data that I don’t want to delete prior to my analysis. What are the best options available for me to retain these partially missing cases?
Missing data are a common problem faced by nearly all data analysts, particularly with the increasing emphasis on the collection of repeated assessments over time.…
