[Rasch] compare nested models in Facets

Iasonas Lamprianou liasonas at cytanet.com.cy
Wed Dec 21 20:47:55 EST 2011

Thank you Mike

Is my plan (to compare the two models as I described it, please see below) reasonable?

I had asked: 
"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?"

----- Original Message Follows -----
From: Mike Linacre <rmt at rasch.org>
To: <rasch at acer.edu.au>
Subject: Re: [Rasch] compare nested models in Facets
Date: Wed, 21 Dec 2011 19:22:32 +1300
> Iasonas asked: "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?"
> Answer: That information, described in 
> http://www.winsteps.com/facetman/index.htm?table5.htm , is obtained by 
> accumulating response-level information. The response-level information is 
> in the Facets "Residual file=".
> OK?
> Mike L.
> Mike Linacre
> Editor, Rasch Measurement Transactions
> rmt at rasch.org www.rasch.org/rmt/ Latest RMT: 25:3 Winter 2011
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