[Rasch] Rasch fit and unidimensionality

Fraser Rew Fraser.Rew at nzqa.govt.nz
Thu Jul 10 12:42:38 EST 2008


In response to Juanito's comments: for the Rasch model to fit there are
many criteria that must be satisfied,  unidimensionality being one.
Therefore, if the model fits the data, the test is unidimensional (as
well as meeting other criteria). 

Conversely, if the model does not fit the data, it may be because the
test is not unidimensional or it may be because one of the other
criteria was not met - we must seek further information.

Regards

Fraser

Fraser Rew
Researcher/Data Analyst
Qualificiations Division
DDI: 04 463 4368
Extn: 4368

www.nzqa.govt.nz

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Today's Topics:

   1. Fit & Dimensionality (Anthony James)
   2. Fit & Dimensionality (Anthony James)
   3. Fit & Dimensionality (Anthony James)


----------------------------------------------------------------------

Message: 1
Date: Wed, 9 Jul 2008 00:03:54 -0700 (PDT)
From: Anthony James <luckyantonio2003 at yahoo.com>
Subject: [Rasch] Fit & Dimensionality
To: rasch at acer.edu.au 
Message-ID: <91214.22960.qm at web50805.mail.re2.yahoo.com>
Content-Type: text/plain; charset="iso-8859-1"

Hi all,
I have found something interesting:
"...a Rasch model fit impressively supports unidimensionality of a
test,2 but in reverse, a Rasch model misfit does not necessarily
contradict
unidimensionality. The appropriateness of the scoring rule has merely
been invalidated
in the latter case" (p.381).
á
This is very different to what I have learned.
Any ideas?
á
It is here:
http://www.informaworld.com/smpp/content~content=a785034366~db=all 
á
Cheers
Anthony


      
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Message: 2
Date: Wed, 9 Jul 2008 00:03:55 -0700 (PDT)
From: Anthony James <luckyantonio2003 at yahoo.com>
Subject: [Rasch] Fit & Dimensionality
To: rasch at acer.edu.au 
Message-ID: <841136.63386.qm at web50810.mail.re2.yahoo.com>
Content-Type: text/plain; charset="iso-8859-1"

Hi all,
I have found something interesting:
"...a Rasch model fit impressively supports unidimensionality of a
test,2 but in reverse, a Rasch model misfit does not necessarily
contradict
unidimensionality. The appropriateness of the scoring rule has merely
been invalidated
in the latter case" (p.381).
á
This is very different to what I have learned.
Any ideas?
á
It is here:
http://www.informaworld.com/smpp/content~content=a785034366~db=all 
á
Cheers
Anthony


      
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------------------------------

Message: 3
Date: Wed, 9 Jul 2008 00:03:56 -0700 (PDT)
From: Anthony James <luckyantonio2003 at yahoo.com>
Subject: [Rasch] Fit & Dimensionality
To: rasch at acer.edu.au 
Message-ID: <219672.65446.qm at web50811.mail.re2.yahoo.com>
Content-Type: text/plain; charset="iso-8859-1"

Hi all,
I have found something interesting:
"...a Rasch model fit impressively supports unidimensionality of a
test,2 but in reverse, a Rasch model misfit does not necessarily
contradict
unidimensionality. The appropriateness of the scoring rule has merely
been invalidated
in the latter case" (p.381).
á
This is very different to what I have learned.
Any ideas?
á
It is here:
http://www.informaworld.com/smpp/content~content
=a785034366~db=all 
á
Cheers
Anthony


      
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