Negative chi-square difference PreviousNext
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 Cristina Sturaro posted on Monday, June 16, 2008 - 6:02 am
Hi Bengt and Linda,

I'm testing for gender differences an autoregressive cross-lagged model using a multiple group model (boys vs. girls). First I let the parameters free for boys and girls. Then I rerun the model with the parameter estimates equal between boys and girls. As a result, the chi-square of the model with free estimates has a higher chi-square (and of course fewer Df) than the one with the fixed parameters, resulting in a negative chi-square difference value.

Is a negative chi-square difference acceptable? And if yes, shall I report the value with the negative sign?

Thanks.
 Linda K. Muthen posted on Monday, June 16, 2008 - 9:46 am
If you are using MLM or MLR, this can happen and the results are not meaningful.
 Cristina Sturaro posted on Wednesday, June 18, 2008 - 12:45 am
Hi Linda,

thank you for the fast reply.

Could you please clarify me something?

What did you mean by "the results are not meaningful"? Does it mean that the chi-square test is not valid? Or that the differences I've found between boys and girls in the free estimated model are not significant and are the results of the reduced sample sizes of model male and female? Or maybe something else?

Thank you
 Linda K. Muthen posted on Wednesday, June 18, 2008 - 8:49 am
Yes, the test is not working correctly so it should not be interpreted.
 uclaalice86 posted on Wednesday, September 17, 2008 - 10:20 pm
Hi,
I am running into the same issue as mentioned above while using MLR. If the chi-sq test cannot be interpreted, what are alternatives to test fixing just one parameter in my model?
thanks!
 Linda K. Muthen posted on Thursday, September 18, 2008 - 6:33 am
You can use MODEL TEST. See the user's guide for further information.
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