Correlations Greater Than 1.0 in Class PreviousNext
Mplus Discussion > Latent Variable Mixture Modeling >
 Nicholas Allan posted on Wednesday, August 21, 2013 - 8:37 am

I am conducting factor mixture modeling, with covariances free across classes. In two of my classes (in a four-class solution), I get an error message THE LATENT VARIABLE COVARIANCE MATRIX (PSI) IN CLASS 2 IS NOT POSITIVE DEFINITE...and the same message for CLASS 2. It appears that this is occurring because of a correlation greater than 1 between two of my factors. Does this mean that there is a problem with my model, or might it mean that in two of my classes, these factors are actually not different?

As a follow-up, if it is that these factors are better-represented as a single factor in two of the classes, would it be appropriate to model that as such (i.e., creating a model where two classes include these separate factors as a single factor)?

Thanks in advance,
 Linda K. Muthen posted on Wednesday, August 21, 2013 - 9:41 am
Yes, there is a problem with the model and yes, the two factors may not be different in some classes. You can have different factors in different classes.
 Nicholas Allan posted on Sunday, August 25, 2013 - 12:59 pm
Hi Linda,

Thanks for your quick response. I am attempting to create different factors by classes. I am not sure how to model it though. I want to restrict two factors to a single factor in one of my classes but allow the factors to be separate in the other classes. When I tried to model the factors independently in each class, without listing them in the %overall% model, Mplus doesn't seem to recognize the factors that I created. Is there another approach. I was thinking that I could set the correlation between the two factors to one in the class that I wanted them to be the same, and then set the correlations between those factors and other factors to be equal. Would this work, or is there another way that I could model different factors in different classes?

Thanks for your help,
Nik Allan
 Linda K. Muthen posted on Monday, August 26, 2013 - 11:33 am
Send us a output with your best try and your license number to
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