# Exploratory Factor Analysis with Mplus

Previously, I discussed how to do a confirmatory factor analysis with Mplus. What if you aren’t sure what variables should load on what factor? Then you are doing an exploratory factor analysis. Really, you should probably do the exploratory factor analysis first unless you have some very large body of research behind you saying that there should be X number of factors and these exact variables should load on them. If you’re analyzing the Weschler Intelligence Scale, you probably could skip the exploratory step. For everyone else …. here is how you do an exploratory factor analysis with Mplus.

TITLE : Exploratory Factor Analysis ;
Data:  FILE IS ‘values.dat’ ;
VARIABLE: NAMES ARE q1f1 q2f1 q3f1 q1f2 q2f2 q3f2 ;
ANALYSIS: TYPE = EFA 1 3 ;
ESTIMATOR = ML ;

When no rotation is specified using the ROTATION option of the ANALYSIS command, the default oblique GEOMIN rotation is used.

The fourth statement is new. Like the other statements, you need to follow the ANALYSIS key word with a colon and end each statement in the command (or if you are familiar with SAS, think of it as a procedure) with a semi-colon.

TYPE = EFA 1 3 ;

Requests an exploratory factor analysis with a 1 factor solution, 2-factor solution and 3-factor solution.  Of course, depending upon your own study, you can request whatever solutions you want. This is really useful because often in an exploratory study you aren’t quite sure of the number of factors. Maybe it is two or maybe three will work better. Mplus gives you a really simple way to request multiple solutions and compare them. I’ll talk more about that in the next post.

ESTIMATOR = ML ;

requests maximum likelihood estimation.

If you are interested in factor analysis at all, there is a really good video on the Mplus site. Far more of it discusses exploratory and confirmatory factor analysis – methods, goodness of fit tests, equations, interpretation of factor matrix – than Mplus, which as you can see, is pretty easy, so even if you are using some other software the video is definitely worth checking out.