How can I estimate statistical power for a structural equation model?

July 6, 2019

This is a question that often arises when using structural equation models in practice, sometimes once a study is completed but more often in the planning phase of a future study. To think about power, we must first consider ways in which we can make errors in hypothesis testing (Cohen, 1992). Briefly, the Type I…

What are modification indices and should I use them when fitting SEMs to my own data?

June 10, 2019

This is a great question and is one that prompts much disagreement among quantitative methodologists. Nearly all confirmatory factor analysis or structural equation models impose some kind of restrictions on the number parameters to be estimated. Usually, some parameters are set to zero (and thus not estimated at all), but sometimes restrictions come in the…

Do you have any materials that demonstrate how to estimate structural equation models using lavaan in R?

April 24, 2019

This is a question we often hear, particularly from students and junior researchers who don’t have access to sometimes expensive commercial software for fitting structural equation models. It is possible to estimate a wide array of SEMs, ranging from simple path models to fully latent SEMs to growth curve models and beyond, using the lavaan…

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

February 18, 2019

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 term “growth modeling” refers to a variety of statistical methods that allow for the estimation of inter-individual (or between-person) differences in intra-individual (or within-person) change. Often, the function describing within-person…

Can I estimate an SEM if the sample data are not normally distributed?

January 23, 2019

Continuous distributions are typically described by their mean (central tendency), variance (spread), skew (asymmetry), and kurtosis (thickness of tails). A normal distribution assumes a skew and kurtosis of zero, but truly normal distributions are rare in practice. Unfortunately, the fitting of standard SEMs to non-normal data can result in inflated model test statistics (leading models…

How do I know if my structural equation model fits the data well?

January 11, 2019

This is one of the most common questions we receive and, unfortunately, there are no quick answers. However, there are some initial guidelines that can be followed when assessing the fit of an SEM. For most SEMs, the goal of the analysis is to define a model that results in predicted values of the summary…

Summer Workshop Schedule for 2018

October 10, 2017

We are pleased to announce our workshop schedule for this summer: May 9-11: Network Analysis May 21-25: Multilevel Modeling June 4-8: Latent Class/Cluster Analysis and Mixture Modeling June 18-22: Structural Equation Modeling June 25-29: Longitudinal Structural Equation Modeling   This year, we will be holding all workshops at the Chapel Hill-Carrboro Hampton Inn & Suites,…

Growth modeling within a structural equation modeling framework

March 31, 2017

In a prior episode of Office Hours, Patrick explored “Growth modeling in a multilevel modeling framework.” In the current episode he discusses how growth models can also be estimated within the structural equation modeling (SEM) framework. He begins with a brief review of the confirmatory factor analysis model and describes this as the foundation of…

Why use a Structural Equation Model?

March 23, 2017

In this edition of CBA Office Hours, Dan discusses some of the principal advantages of the structural equation model (SEM) relative to more traditional data analytic approaches like the linear regression model. Advantages include the ability to account for measurement error when estimating effects, test the fit of the model to the data, and specify statistical…