[Rasch] Rasch to G-theory

Iasonas Lamprianou liasonas at cytanet.com.cy
Fri Apr 20 03:29:58 EST 2012


Than you very much Mike

Jason

----- Original Message Follows -----
From: Mike Linacre <rmt at rasch.org>
To: <rasch at acer.edu.au>
Subject: Re: [Rasch] Rasch to G-theory
Date: Tue, 10 Apr 2012 19:43:51 +1300
> Jason:
> 
> The variances needed to compute a Rasch-based equivalent to a 
> Generalizability Coefficient (G) are in Facets Tables 5 and 7.
> 
> My apologies that the "explained variance" computations at 
> www.winsteps.com/facetman/table5.htm do not show the last step in the 
> computation. It is:
> 
> G = (Explained variance% by target facet) / 100
> 
> Please verify this value of G makes sense for your data. A more specific 
> Generalizability Coefficient may be more meaningful to your audience. 
> Variance terms similar to 
> http://www.stanford.edu/dept/SUSE/SEAL/Reports_Papers/ReliabCoefsGTheoryHdbk.pdf 
> page 20 can be extracted from Facets output. These can be used to compute a 
> more focused Generalizability Coefficient.
> 
> Mike L.
> 
> 
> At 4/10/2012, you wrote:
> >can anyone direct me to a paper which explains how to use Rasch measured 
> >reported by Facets to compare the results with G-theory estimates? For 
> >example, I can read in the Facets output the sd of item measures, the sd 
> >of rater measures and the sd of person measures. How can I produce an 
> >index which is similar to the variance attributed to markers as computed 
> >in generalizability theory? Or maybe this is not possible? A good search 
> >on the internet did not help me a lot, although I reached a paper by 
> >Macmillan (2000) which, unfortunately, I cannot have access.
> 
> Mike Linacre
> Editor, Rasch Measurement Transactions
> rmt at rasch.org www.rasch.org/rmt/ Latest RMT: 25:4 Spring 2012
> 
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