IRT and Confusion about Rasch Measurement

The International Journal of Educational and Psychological Assessment contains papers relating to Classical Test Theory (CTT), Item Response Theory (IRT) and Rasch measurement. Unfortunately these papers present a confusing perspective on Rasch measurement. For instance,

1. Cutoff Scores: The Basic Angoff Method and the Item Response Theory Method. Niclie Tiratira. tijepa.books.officelive.com/Documents/article5v1.pdf

This articles employs Bigsteps and Winsteps, without citing the sources, in an IRT context, and reports results with no sense of the fingernails-on-the-blackboard dissonance infit and outfit have relative to IRT.

2. The Measurement of Change in Groups and Individuals With Particular Reference to the Value of Change Scores: A New IRT-Based Methodology for the Assessment of Treatment Effects. Jörg A. Prieler and John Raven. tijepa.books.officelive.com/Documents/A3V3_TIJEPA.pdf

This article asks and answers the following questions:

Question 1. Does the portrayal of parallel item characteristic curves (ICCs) in Rasch computer analysis output mislead many into thinking the item difficulty order is independent of ability?
Their answer: Yes. But the Rasch answer: No. Rasch analysis deliberately constructs item difficulties which are as independent as statistically possible of ability.

Question 2. Do the crossing ICCs in a 3-parameter IRT analysis indicate that the appropriate model for these data is one that describes the interactions making item and person estimates dependent on one another?
Their answer: Yes. But the Rasch answer: No. Crossing ICCs are never an appropriate model (except for some polytomous models.) Construct validity demands that the item difficulty hierarchy is invariant across person abilities.

Question 3: Are the "most popular versions of Item Response Theory" often loosely referred to as "the Rasch model"?
Their answer: Yes. But the Rasch answer: No. IRT is a descriptive statistical methodology originated by Frederic Lord. Rasch analysis is a prescriptive measurement methodology originated by Georg Rasch. One of Lord's IRT models resembles a Rasch model.

Comment: What chaos! The force of the academically-dominant IRT paradigm's influence is truly impressive: it is able to make people see things that don't exist, and to let them ignore existing things that don't fit with their preconceptions. How will these kinds of misconceptions ever be corrected? Will it all come out in the wash at some point down the road when invariance, sufficiency and additivity are demanded as basic elements of credible psychometric measurement?

William P. Fisher, Jr.


IRT and Confusion about Rasch Measurement, W.P. Fisher, Jr. ... Rasch Measurement Transactions, 2010, 24:2 p. 1288




Rasch Publications
Rasch Measurement Transactions (free, online) Rasch Measurement research papers (free, online) Probabilistic Models for Some Intelligence and Attainment Tests, Georg Rasch Applying the Rasch Model 3rd. Ed., Bond & Fox Best Test Design, Wright & Stone
Rating Scale Analysis, Wright & Masters Introduction to Rasch Measurement, E. Smith & R. Smith Introduction to Many-Facet Rasch Measurement, Thomas Eckes Invariant Measurement: Using Rasch Models in the Social, Behavioral, and Health Sciences, George Engelhard, Jr. Statistical Analyses for Language Testers, Rita Green
Rasch Models: Foundations, Recent Developments, and Applications, Fischer & Molenaar Journal of Applied Measurement Rasch models for measurement, David Andrich Constructing Measures, Mark Wilson Rasch Analysis in the Human Sciences, Boone, Stave, Yale
in Spanish: Análisis de Rasch para todos, Agustín Tristán Mediciones, Posicionamientos y Diagnósticos Competitivos, Juan Ramón Oreja Rodríguez

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