Error message: Latent Factors correla... PreviousNext
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Message/Author
 Jessica Oschwald posted on Thursday, July 21, 2016 - 11:53 am
Hello,

My goal is to fit a LCSM over 3 measurement time points . To establish basic model structure, I first fit a latent state model with three time points and autocorrelated neighboring error variables:

MODEL:
reas1 by LPS3_T1 LPS4_T1;
reas2 by LPS3_T2 LPS4_T2;
reas3 by LPS3_T3 LPS4_T3;

! specification of autocorrelated error variables
LPS4_T1 with LPS4_T2;
LPS4_T2 with LPS4_T3;
LPS3_T1 with LPS3_T2;
LPS3_T2 with LPS3_T3;

I received the following error message:

WARNING: THE LATENT VARIABLE COVARIANCE MATRIX (PSI) IS NOT POSITIVE DEFINITE. THIS COULD INDICATE A NEGATIVE/RESIDUAL VARIANCE FOR A LATENT VARIABLE, A CORRELATION GREATER OR EQUAL TO ONE BETWEEN TWO LATENT VARIABLES, OR A LINEAR DEPENDENCY AMONG MORE THAN TWO LATENT VARIABLES. CHECK THE TECH4 OUTPUT FOR MORE INFORMATION. PROBLEM INVOLVING VARIABLE REAS2.

The same happened for other factors with two indicators that I wanted to fit - but not for a factor with three indicators (this fit very well). The same problem occurred for all models: the latent variables were correlated > than 1. When I started to fix these correlations to 1, the problem just shifted to other variables and yielded negative variances...

I wonder if the problem lies in my model specification for the two-indicator solution, or is it possible that this simple model does not fit my data?

Thanks for your help!
Jessica
 Linda K. Muthen posted on Thursday, July 21, 2016 - 2:02 pm
This message usually means that the model needs to be changed.
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