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ljc posted on Friday, May 31, 2013  8:20 pm



On slide 100 of the Short Course,Topic 7 (Multilevel modeling of crosssectional data), there is a Multilevel IRT model. Where can I find an example of MPlus Code for a model like this? 


See UG ex 9.7. 

ljc posted on Monday, June 03, 2013  4:44 pm



I am not sure if this make sense, but I think the model in example 9.7 has random intercepts for the items and I only want random intercepts for the the factor/theta. Even if the random intercepts for the items are necessary, I would like an intraclass correlation for the the factor, a mean and variance for the factor and if possible, cluster level estimates of the factor/theta. Is it possible to get this? Thank you. 


See slides 2831 of my recent UConn keynote address which you find on our website. I think the model you are after is the one shown on slide 28. As you see, it involves modifying UG ex 9.7 by setting the loadings equal across levels and fixing the betweenlevel residual variances for the indicators at zero. 

ljc posted on Monday, June 03, 2013  9:05 pm



I could get what I am after by outputing the factor scores from the single level IRT to a dataset and using them as a dependent variable in SAS Proc Mixed. But my understanding is that this is would have problems because the factor scores are shrunken estimates. I just want to use the factor/theta as a dependent variable in a 2 or 3 level model if the icc indicates that I should. Would setting the loadings equal at both levels accomplish this? Will it output an icc for the factor? Thank you. 


You want equal loadings and also zero residual variances for the indicators on Between. icc can be computed from the results as B/(B+W), where B is the betweenlevel factor variance and W is the withinlevel factor variance. When you hold the loadings equal across levels you want to fix the within factor variance and free the between factor variance. 

ljc posted on Tuesday, June 04, 2013  11:13 pm



The slide presentation doesn't have mplus code. Is there sample code available for this? 


You have the Mplus code at http://www.statmodel.com/examples/V7_1examples.shtml see the slide 31 run. 

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