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Dear Muthen & Muthen, I notice that the DIFFTEST option is not available in a multilevel CFA. My analysis uses a saturated withinlevel model with a 4 factor measurement model fit to the between level. The estimator is WLSMV with categorical observables. So that I may assess the improvement in fit for my between level model when compared to the same between level model with an error covariance freed, is there some way that I can do the DIFFTEST manually without being exposed to any complicated mathmatics or horrible equations? Kind regards, Jonahton 


I am afraid it involves complicated statistics. The easiest way out is to use WLSM instead of WLSMV. 


Cheers for this Bengt. When you say that the easiest way out is to use WLSM instead of WLSMV, am I correct in assuming that when using WLSM that a comparison of nested models is simply a matter of computing the difference between the chisquare and degrees of freedom for the two models in the same way that you would for normal theory ML? Jonathon 


Right. 


Ok this is a little confusing Bengt, After reading page 367 of the User manual and the standard MPLUS output that is printed below: "The chisquare value for MLM, MLMV, MLR, ULSMV, WLSM and WLSMV cannot be used for chisquare difference tests. MLM, MLR and WLSM chisquare difference testing is described in the Mplus Technical Appendices at www.statmodel.com. See chisquare difference testing in the index of the Mplus User's Guide" Can you reread this thread and my questions and explain this contradiction for me. You answered "right" to my question which read "am I correct in assuming that when using WLSM that a comparison of nested models is simply a matter of computing the difference between the chisquare and degrees of freedom for the two models in the same way that you would for normal theory ML?" Regards, Jonathon 


You need to take the scaling correction factor into account when doing difference testing for WLSM. See ChiSqare Difference Test for MLM and MLR on the website. This applies also to WLSM. 

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