Missing data regression PreviousNext
Mplus Discussion > Missing Data Modeling >
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 Anthony Mancini posted on Tuesday, June 02, 2015 - 12:18 pm
I want to regress a continuous predictor on a categorical variable (4 categories or three dummy coded predictors).

I have missing data on the dependent but obviously not on the IVs. The N = 368.

My purpose is to examine group differences and to use maximum likelihood to address missing data ( focusing specifically on one of the groups as the reference).

I have specified the variances in the model and it produces interpretable results. But I keep getting a non-positive definite message.
THE MODEL ESTIMATION TERMINATED NORMALLY
THE STANDARD ERRORS OF THE MODEL PARAMETER ESTIMATES MAY NOT BE TRUSTWORTHY FOR SOME PARAMETERS DUE TO A NON-POSITIVE DEFINITE FIRST-ORDER DERIVATIVE PRODUCT MATRIX.

This is a very simple model. The results make sense and my interest is in the resulting estimates. Do I need to address this error? If so, how can I improve the model to accommodate the error?

Thanks very much.
 Bengt O. Muthen posted on Tuesday, June 02, 2015 - 4:49 pm
Perhaps you are including your dummies in the model in the sense of having their parameters estimated. In which case the message can be ignored.
 Anthony Mancini posted on Tuesday, June 02, 2015 - 7:03 pm
Yes, I believe that is it.

Thank you, Bengt.
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