RMSR as an extraction criterion PreviousNext
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 Florian Fiedler posted on Monday, November 28, 2005 - 4:41 am
Dear MPlus-team,

would you say, it's possible to use the RMSR fit index to make a decision on how many factors one should include in a model?

I'm conducting an EFA (estim. ULS) and according to Eigenvalue criteria I should assume 2 factors but the RMSR is much (seems to be significant) better when assuming 3 factors. So I'm thinking about comparing the fit indices with something like a X difference test - of course without Xs but perhaps based on RMSR. Would you say that's a feasible way?

Thanks a lot for your support and advice.
 Linda K. Muthen posted on Monday, November 28, 2005 - 4:45 pm
I'm not sure if your indicators are continuous or categorical but if you use ML or WLSMV, you will obtain chi-square and RMSEA in addition to RMSR.
 Florian Fiedler posted on Tuesday, November 29, 2005 - 12:47 am
Dear Linda,

that sounds good to me. I'm (still) following Grilli and Rampichini (2004).

Step 2 would be an EFA on the polychoric correlation matrix. -> WLSMV instead of ULS?

Step 3 requires seperate analysis of the between and pooled-within matrices. My indicators are actually ordinal, but the seperated matrices are only available when I treat them as being continuous ... So I've to conduct the EFA on the two matrices based on continuous data. -> ML instead of ULS?

Can I use the obtained RMSEA directly or would you recommend doing two CFAs with DIFFTEST?
 Linda K. Muthen posted on Tuesday, November 29, 2005 - 6:55 am
Yes.

Yes.

If your outcomes do not have strong floor or ceiling effects, it you have 5 categories you may want to treat them as continuous at least for these preliminary studies.

I'm not clear on your last question.
 Florian Fiedler posted on Tuesday, November 29, 2005 - 8:48 am
To make a decision in favour of a certain number of factors I want take the fit into account as well as an Eigenvalue criterion. So I'd have to compare two factor solutions. The EFA outputs provides fit indices as well so I thought about comparing them. I just talked to my mentor and we decided to model two CFAs according to the EFA outcome and comparing the CFA fit indices afterwards.

So the question is answered in a way. I'll get fit indices for the CFA models and only take those from the EFA with a one factor-solution.

Thank you very much - for further comments on our model selection strategy, too.
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