Nonpositive Trace PreviousNext
Mplus Discussion > Multilevel Data/Complex Sample >
 Anthony Coy posted on Thursday, October 06, 2011 - 4:38 pm

I am working on examining partner effects (similar to the actor-partner interdependence model) using observed categorical variables and interactions of those variables. Note: I created my interaction terms in the design statement. When I run the model, it says that it terminated normally and provides me with the standard output but doesn't provide the chi-squared, CFI, TLI or RMSEA statistics with the message that, "ROBUST CHI-SQUARE IS NOT DEFINED DUE TO NONPOSITIVE TRACE." This discussion board is the only place I've seen a nonpos trace mentioned and I'm not sure what it means. Any help you could provide would be greatly appreciated!

 Tihomir Asparouhov posted on Friday, October 07, 2011 - 3:52 pm
Formula (106) in the technical appendices is where the problem occurs. See

These formulas are asymptotic and can run into such problems for small sample sizes. There may be other things that cause this problem - perhaps sever model misspecification.

One way to proceed is to change the estimator. You can try estimator=ulsmv or wls.

You can send your example to for possible further insights.
Back to top
Add Your Message Here
Username: Posting Information:
This is a private posting area. Only registered users and moderators may post messages here.
Options: Enable HTML code in message
Automatically activate URLs in message