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Testing Unidimensionality in Polytomous Rasch Models

Published online by Cambridge University Press:  01 January 2025

Karl Bang Christensen*
Affiliation:
National Institute of Occupational Health, Denmark Department of Biostatistics, University of Copenhagen
Jakob Bue Bjorner
Affiliation:
National Institute of Occupational Health, Denmark
Svend Kreiner
Affiliation:
Department of Biostatistics, University of Copenhagen
Jørgen Holm Petersen
Affiliation:
Department of Biostatistics, University of Copenhagen
*
Requests for reprints should be sent to Karl Bang Christensen, National Institute of Occupational Health, Lersø Parkallé 105, 2100 KBH Ø, DENMARK. E-Mail: kbc@ami.dk

Abstract

A fundamental assumption of most IRT models is that items measure the same unidimensional latent construct. For the polytomous Rasch model two ways of testing this assumption against specific multidimensional alternatives are discussed. One, a marginal approach assuming a multidimensional parametric latent variable distribution, and, two, a conditional approach with no distributional assumptions about the latent variable. The second approach generalizes the Martin-Löf test for the dichotomous Rasch model in two ways: to polytomous items and to a test against an alternative that may have more than two dimensions. A study on occupational health is used to motivate and illustrate the methods.

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Type
Articles
Copyright
Copyright © 2002 The Psychometric Society

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