R help - Feb 2009 - Fit indexes in SEM with categorical data + ML estimation

Hello,


It has been found that SEM analysis using polychoric correlations + maximum
likelihood estimator produces incorrect test statistics and standard errors
(e.g., Flora, D. B., & Curran, P. J. (2004). An Empirical Evaluation of
Alternative Methods of Estimation for Con?rmatory Factor Analysis With
Ordinal Data. Psychological Methods, 9(4), 466-491).

Standard errors can be dealt with by using bootstrap estimations. But, I was
wondering how the fit indexes in the SEM package were estimated when the
observed variables are categorical (ordinal or/and binary) and when one is
using polychoric correlation (hetcor in polycor package) in combination with
ML. Does SEM use the Satorra-Bentler rescaled Chi-square for instance?
I look in previous posts but couldn't find what i am looking for (hope i
looked well enough!).


Cheers,
Dorothee

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Hey, Dorothee.  SEM does not use the S-B chi squared index.  If you want to
use it, however, I have some methods written for the Satorra-Bentler Chi
Square test in the sem.additions package over at r-forge.

To install it directly within R type
install.packages("sem.additions",repos="http://R-Forge.R-project.org")

For more details, see http://r-forge.r-project.org/projects/sem-additions/



Dorothee wrote:
> 
> Hello,
> 
> 
> It has been found that SEM analysis using polychoric correlations +
> maximum likelihood estimator produces incorrect test statistics and
> standard errors (e.g., Flora, D. B., & Curran, P. J. (2004). An
Empirical
> Evaluation of Alternative Methods of Estimation for Con?rmatory Factor
> Analysis With Ordinal Data. Psychological Methods, 9(4), 466-491).
> 
> Standard errors can be dealt with by using bootstrap estimations. But, I
> was wondering how the fit indexes in the SEM package were estimated when
> the observed variables are categorical (ordinal or/and binary) and when
> one is using polychoric correlation (hetcor in polycor package) in
> combination with ML. Does SEM use the Satorra-Bentler rescaled Chi-square
> for instance?
> I look in previous posts but couldn't find what i am looking for (hope
i
> looked well enough!).
> 
> 
> Cheers,
> Dorothee
> 
> 
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