[Rasch] Empirical order & Theoretical order

Andrew Kyngdon AKyngdon at lexile.com
Fri Nov 5 15:44:36 EST 2010


Parisa,

I think your Point 1 is valid (as is 2 and 3, of course). What is meant casually by "Rasch model" is the simple dichotomous item case, when in fact there exists a whole family of Rasch models (e.g., paired comparison, Poisson Counts, extended frame of reference). It is quite plausible that one member of this family is more suitable than another for a given empirical / theoretical situation.

You can shape a Rasch model to be more in accordance with theory. Take the Lexile Framework for Reading, for example. This psychometric framework uses a modified version of the simple dichotomous item Rasch model. When person reading ability and item difficulty are equal, the item response probability is .75. This was done because it would be unlikely that a reader has genuinely understood the content of an "embedded sentence cloze" reading item if the response probability was the conventional .5. This modification is not to the detriment of raw score sufficiency or invariant comparisons.

There is more scope for stimulus - theory -  model interplay than what is commonly perceived in psychometrics. Look at utility theory, for example.

Cheers,

Andrew

From: rasch-bounces at acer.edu.au [mailto:rasch-bounces at acer.edu.au] On Behalf Of Parisa Daftari Fard
Sent: Wednesday, 3 November 2010 9:53 AM
To: rasch list
Subject: Re: [Rasch] Empirical order & Theoretical order

The topic sounds interesting. I believe that When we do not have an agreement between Rach model and Theoretical model, there are three possibilities

1.  Rasch model requires revision
2.  Theory requires revision
3.  Items requires revision

One of the 1, 2, or 3 should be revised.

Best,
Parisa

--- On Tue, 11/2/10, Trevor Bond <trevor.bond at jcu.edu.au> wrote:

From: Trevor Bond <trevor.bond at jcu.edu.au>
Subject: Re: [Rasch] Empirical order & Theoretical order
To: "Raschlist" <rasch at acer.edu.au>
Date: Tuesday, November 2, 2010, 11:18 AM
In a nutshell

you might use Rasch info to reject items

but who wrote the items?

Unlikely , it was the theorist...and even if it was
is the theorist a good item writer (not equivalent skills)?

over to you...

Prof Trevor G BOND
Adjunct Professor
School of Education
James Cook University
AUSTRALIA
mob: +61 416 82 70 83
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