[Rasch] Incredible comments on Rasch

matt.schulz at act.org matt.schulz at act.org
Sat Sep 30 07:43:06 EST 2006


The points about additional validity evidence being needed are well taken,
but is that what the review is saying?  Twice, the review states that Rasch
modeling is "not appropriate".  Insufficient, yes.  But inappropriate?  It
is conceivable that one would not expect a collection of items to define a
unidimensional scale.  Even in that case, a Rasch analysis would be
inappropriate only if the items were a given, one had no opportunity to
revise the set of items, and one had no intention of interpreting measures
with reference to *which* items a respondent probably endorsed.   How is
the scale intended to be used?  That largely determines whether a Rasch
analysis is "appropriate."

Also, the review states that "items on an attitude...do not have a linear
order."  I think the reviewer is either misinformed or uninformed on about
the general suitability of the Rasch model for attitude measurement, but
without more knowledge of the items and the how the measure would be used
in this particular case, it's hard to tell if the Rasch model is
"inappropriate."

Matthew Schulz
Department of Statistical Research
ACT, Inc.
Ph. 319-337-1468
matt.schulz at act.org


                                                                                                                                       
                      "Eric Wong"                                                                                                      
                      <mcwong at cuhk.edu.        To:       <rasch at acer.edu.au>                                                           
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                      09/29/2006 04:16                                                                                                 
                      AM                                                                                                               
                                                                                                                                       
                                                                                                                                       




      Dear all,

      Unbelievable comments from reviewers of a research grant review
      board:

      "The questionnaire should be shortened. The proposed validation
      analysis (using Rasch modelling) is not appropriate for a
      questionnaire focusing on attitude and behaviour and should be
      revised."

      "The methods proposed for the adpatation of the content of the IMAQ
      (the questionnaire) are well written, but Rasch analysis for the
      valdiation/reduction of items is not appropriate because the items on
      attitude or usage do not have a linear order, unlike educational
      assessment. More standard methods, such as know group comparison or
      concurrent validity, for validating the construct/criterion validity
      of the IMAQ should be used."

      Any comments?

      Eric



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