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dewant2 posted on Thursday, March 24, 2005 - 1:09 pm
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HI, I'm pretty new to mplus and have been trying to model growth of a continuous variable over time in a mixture analysis. Orgiinally I set each of the 4 time periods to 0,1,3,and6 (the data collection periods) and the model ran but gave me the warning: WARNING: THE RESIDUAL COVARIANCE MATRIX (PSI) IN CLASS 1IS NOT POSITIVE DEFINITE. PROBLEM INVOLVING VARIABLE S. I tried freeing up the parameters and changing the number of latent classes (against my judgement and the indices fit) but no matter what, I get the same warnings about the slope in each latent class. example with 2 free parameters MODEL: %OVERALL% i s | CESDM0@0 CESDM1@1 CESDM3* CESDM6*; THE MODEL ESTIMATION TERMINATED NORMALLY WARNING: THE RESIDUAL COVARIANCE MATRIX (PSI) IN CLASS 1 (...2 3 and 4) IS NOT POSITIVE DEFINITE. PROBLEM INVOLVING VARIABLE S. Any suggestions to get correct the model to remove the warning? Thank you so much |
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bmuthen posted on Thursday, March 24, 2005 - 1:37 pm
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You should update to version 3.12 where this message is explicated further to suggest reasons for the problem. E.g. you may have a zero variance for s, or s may be perfectly correlated with i for some reason (see Tech4). Often when doing growth mixtures, the within-class variation of s is rather small because the classes capture a majority of the variation. |
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