SMABS 2004 Jena University
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European Association of Methodology

Department of methodology and evaluation research

Jena University

Contributions: Abstract

Analysis of parameter invariance through Rasch model fit

Pablo Holgado-Tello Juan Carlos Surez Maribel Barbero
Universidad Nacional de Educacion a Distancia
Pedro Prieto
University of La Laguna
Salvador Chacn-Moscoso
University of Sevilla

The property of invariance of item and ability parameters is the cornerstone of IRT and its major distinction form classical test theory. However, since this advantage is not always found in practical research (Barbero, Prieto, Surez y San Lus, 2001, Fan, 1998; Gil, Surez y Martnez rias, 1999 y Stage, 1999), appropriate methods are needed in order to establish whether this property is met in empirical work.

In a recent work by Surez et al (2002) the use of Lord's Chi-Square test, usually applied in DIF studies, is proposed for the analysis of the invariance property in the two-parameter logistic model. In this presentation, several simulation studies are conducted in order to estimate the fit of the Rasch model under different conditions through the use of Lord's Chi-Square test applied to the study of parameter invariance. First results seem to confirm this method as a good way to ensure the good fit of the Rasch model to a set of data.