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The Rasch Rating Model and the Disordered Threshold Controversy

Adams, Raymond J and Wu, Margaret and Wilson, Mark (2012) The Rasch Rating Model and the Disordered Threshold Controversy. Educational and Psychological Measurement, 72 (4). pp. 547-573. ISSN 0013-1644 (print) 1552-3888 (online)

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Abstract

The Rasch rating (or partial credit) model is a widely applied item response model that is used to model ordinal observed variables that are assumed to collectively reflect a common latent variable. In the application of the model there is considerable controversy surrounding the assessment of fit. This controversy is most notable when the set of parameters that are associated with the categories of an item have estimates that are not ordered in value in the same order as the categories. Some consider this disordering to be inconsistent with the intended order of the response categories in a variable and often term it reversed deltas. This article examines a variety of derivations of the model to illuminate the controversy. The examination of the derivations shows that the so-called parameter disorder and order of the response categories are separate phenomena. When the data fit the Rasch rating model the response categories are ordered regardless of the (order of the) values of the parameter estimates. In summary, reversed deltas are not necessarily evidence of a problem. In fact the reversed deltas phenomenon is indicative of specific patterns in the relative numbers of respondents in each category. When there are preferences about such relative numbers in categories, the patterns of deltas may be a useful diagnostic.

Item Type: Article
Uncontrolled Keywords: ResPubID25702, partial credit model, Rasch model, Rasch rating model
Subjects: FOR Classification > 1701 Psychology
Faculty/School/Research Centre/Department > College of Education
Depositing User: Yimin Zeng
Date Deposited: 22 Jul 2014 06:22
Last Modified: 15 Dec 2014 23:21
URI: http://vuir.vu.edu.au/id/eprint/23261
DOI: 10.1177/0013164411432166
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