CFA with PATTERN and dichotomous items PreviousNext
Mplus Discussion > Confirmatory Factor Analysis >
Message/Author
 Christian Lotz posted on Monday, September 26, 2016 - 4:43 am
Hello,

I want to estimate a CFA Modell with one factor. We used a booklet testdesign, so there are missings by design. The Factor is estimated with dichotomous items.

I used the PATTERN option but can't use the CATEGORIAL option.

When I run MPlus, this error message appears:

THE STANDARD ERRORS OF THE MODEL PARA- METER ESTIMATES MAY NOT BE TRUSTWORTHY FOR SOME PARAMETERS DUE TO A NON-POSITIVE DEFINITE FIRST-ORDER DERIVATIVE PRODUCT MATRIX. THIS MAY BE DUE TO THE STARTING
VALUES BUT MAY ALSO BE AN INDICATION OF MODEL NONIDENTIFICATION. THE CONDITION NUMBER IS 0.122D-18. PROBLEM INVOLVING PARAMETER 127.

THIS IS MOST LIKELY DUE TO VARIABLE LV1 BEING DICHOTOMOUS BUT DECLARED AS CONTINUOUS.

How can I declare my items as dichotomous?
 Bengt O. Muthen posted on Monday, September 26, 2016 - 4:01 pm
I would use a multiple-group analysis with groups corresponding to booklets.

The message is typically given for dichotomous IVs and if so it is ignorable.

If this doesn't help, send output to Support along with your license number.
 Maren Lotz posted on Tuesday, September 27, 2016 - 1:54 am
Dear Mr. Muthen,

Quote:
"The message is typically given for dichotomous IVs and if so it is ignorable."

--> is there any paper or something like that with this argument which I can cite?

Best Regards
Maren Lotz
 Bengt O. Muthen posted on Tuesday, September 27, 2016 - 7:54 am
Not that I know. But it gets back to basic facts: For a dichotomous x the mean is p and the variance p(1-p) and therefore the two are mathematically tied. The first-order derivative matrix is therefore not full rank, resulting in the error message.
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