[Rasch] Unidimensionality

Michael Lamport Commons commons at tiac.net
Fri May 9 01:41:12 EST 2008


I am unclear.  If difficulty is decomposable, does that mean Rasch is not a good way to go.

Michael

-----Original Message-----
>From: Trevor Bond <trevor.bond at jcu.edu.au>
>Sent: May 8, 2008 10:59 AM
>To: markus.quandt at gesis.org, rasch at acer.edu.au
>Subject: Re: [Rasch] Unidimensionality
>
>BUT such additional dimensions do not invalidate the use of the Rasch 
>scores, as these have already separated out the ability dimension of 
>interest!
>
>oh - but they do invalidate it as providing MEASURES /(Rasch scores)
>
>N is the sufficient statistic for ability only to the extent that the 
>data fit the model.
>
>remaining structures in the residuals tell us that the Rasch 
>dimension is not all (most / enough) of what is in the data set.
>-- 
>Trevor G BOND Ph D
>Professor and Head of Dept
>Educational Psychology, Counselling & Learning Needs
>D2-2F-01A EPCL Dept.
>Hong Kong Institute of Education
>10 Lo Ping Rd, Tai Po
>New Territories HONG KONG
>http://www.ied.edu.hk/epcl/about/staff_bondt.htm
>Book: 
>http://www.researchmethodsarena.com/books/Applying-the-Rasch-Model-isbn9780805854626
>Voice: (852) 2948 8473
>Fax:  (852) 2948 7983
>Mob:
>_______________________________________________
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My best,

Michael Lamport Commons, Ph.D.

Assistant Clinical Professor
Department of Psychiatry
Harvard Medical School

Program in Psychiatry and the Law
Beth Israel Deaconess Medical Center
commons at tiac.net

http://www.dareassociation.org/
617-497-5270 Telephone
617-491-5270 Fax



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