[Rasch] compare nested models in Facets
liasonas at cytanet.com.cy
Wed Dec 21 17:44:33 EST 2011
I am using Facets, but not the latest version of Windows Facets. As a result, my Facets does not produce information like the following.
Data log-likelihood chi-square = 270479.6875
Approximate degrees of freedom = 62343
Chi-square significance prob. = .0000
Count Mean S.D. Params
Responses used for estimation = 73358 7.40 2.73 11015
Responses in one extreme score = 15 0.13 0.50 5
All Responses = 73373 7.40 2.73 11020
Count of measurable responses = 73373
Raw-score variance of observations = 7.46 100.00%
Variance explained by Rasch measures = 4.58 61.35%
Variance of residuals = 2.89 38.65%
However, I would like to be able to produce this information because it is useful for my analyses. How can I do it without buying the new Facets?
The reason I need this, is to do the following: I run a model with 4 facets and then I used the same data but removed one facet from the analysis. Presumably, if I deduct the "Data log-likelihood chi-square" of the second model from that of the second, then this gives me the improvement of the model fit for df1-df2 where the df is the "Approximate degrees of freedom" for each model. Then, I assume that this is a chi-square with df1-df2 degrees of freedom in order to test if I should actually model the 4th facet or not. Is this procedure correct to test the two (nested?) models? Do we havea reference for this?
Thank you for your support
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