Message/Author 

Kaigang Li posted on Tuesday, July 28, 2009  12:26 am



I am conducting a higher order CFA with 8 1storder factors and 3 2rdorder factors. I ran the following input and get “WARNING: THE LATENT VARIABLE COVARIANCE MATRIX (PSI) IS NOT POSITIVE DEFINITE. …. ” Model: fSE by Q6SEE2 ...; fSSF1 by Q17SSF1 ...; fSSFa2 by Q22SSFA1 ...; fGP by ...; Q33P2 with Q34P3; fENA1 by ...; fENN2 by...; fEN by fENA1 fENN2; !fEn@1.0; fEXP1 by ...; fEXN2 by ...; fEX by fEXP1 fEXN2; The variance of 2rdorder factor(FEN)is negative. Variances FEN 0.037 0.075 0.489 0.625 When fix the variance of FEN to 0 I got the same warning. fEN by fENA1 fENN2; fEn@0; When I fixed FEN to 1.0 and freed fENA1 as fEN by fENA1* fENN2; fEn@1.0; I got the same warning and another error "THE STANDARD ERRORS OF THE MODEL PARAMETER ESTIMATES MAY NOT BE TRUSTWORTHY ...." But when I did not free the first factor with only fixing the FEN to 1.0, the model fit well. fEN by fENA1 fENN2; fEn@1.0; I am not sure if it makes sense. Would you give any suggestion? Thank you very much! Kaigang 


If the secondorder factor has no variance, the model is not appropriate for the data. The following statements should not be used: fEN by fENA1 fENN2; fEn@1.0; In them, you fix the metric of the factor twice by fixing a factor loading to one and the factor variance to one. This is not correct. 

Kaigang Li posted on Tuesday, July 28, 2009  9:11 am



Hi Professor Muthen, Thanks for your quick response. Would you tell me what would be the reason that results in the zero variance since the EFA produced two factors for the FEN scale? I have other secondorder factors which have variances as follows: Variances FSE 1.180 0.148 7.984 0.000 FSS 0.542 0.154 3.528 0.000 FGP 2.136 0.166 12.889 0.000 FEN 0.037 0.075 0.489 0.625 FEX 5.840 2.548 2.292 0.022 May I break down just FEN into two factors without using fEN by fENA1 fENN2; any more, but keep other seondorder factors? Thanks a lot. Kaigang 


How did you do a secondorder EFA? 

Kaigang Li posted on Tuesday, July 28, 2009  7:06 pm



I don't think I have done secondorder EFA, instead I just did firstorder EFA. Should I refer to the example 4.5 and 4.6 in the Mplus guide book for secondorder EFA? Any suggestions for other reference would greatly appreciated. Thank you very much! Kaigang 


I asked because you implied that you had done a secondorder EFA and therefore the secondorder CFA should fit. Given the one secondorder factor has no variance. It should not be included in the model. 

Kaigang Li posted on Wednesday, July 29, 2009  2:02 pm



Sorry about the confusion. I am considering to remove that secondorder factor. Thanks! 

Kaigang Li posted on Wednesday, July 29, 2009  10:04 pm



Professor Muthen, I got another question. I read a very good discussion regarding fit indices for categorical outcomes at http://www.statmodel.com/discussion/messages/23/26.html?1244640406 posted 10 ages ago. I am carrying out SEM with a binary outcome variable using MLR. It seems that so far Mplus still does not provide fit indices for categorical outcomes. I am wondering there is any conclusion on that or there is any alternative way to diagnose model fit with categorical outcomes. Any suggestion and useful references are appreciated. Kaigang 


Chisquare and other related fit statistics are not available when means, variances, and covariances are not sufficient statistics for model estimation. These fit statistics are available for categorical outcomes with weighted least squares estimation. 

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