Useful Reporting of DIF

Major problems with the investigation of differential item functioning (DIF, item bias) are inexplicability and unreproducibility. Merely relying on statistical indicators to identify DIF leaves the analyst at the mercy of idiosyncratic samples of sub-groups. Experts, on the other hand, can discover something biased in every test item. Different experts can even assert that items are biased in different directions!

A combination of statistical, substantive and graphical techniques solves this problem. The Figure illustrates DIF in an "activities of daily living" (ADL) instrument. Looking at an single item, such as "Small-scale Shopping", we could come up with reasons why it is biased against both men and women! But plot all the item difficulties for men against those for women, and the general pattern is clear. Men find it harder to do chores around the house, "Washing", "Cleaning", "Cooking". Women find gross motor activities harder, "Locomotion Outdoors", "Small-scale shopping", "Large-scale shopping". Neutral items are "Simple meal" and "Public transport". Since the bias pattern indicated statistically has a clear substantive meaning that surmounts individual items, we can report the DIF as explicable and likely to be reproduced in continuing use of the instrument.

Gunnar Grimby

Grimby G., Andrén E., Daving Y., Wright B.D. (1998) Dependence and perceived difficulty in daily activities in stroke survivors. Stroke 29, 1843-1849.

Useful reporting of DIF.Grimby G. … Rasch Measurement Transactions, 1998, 12:3 p. 651.

Rasch Books and Publications
Invariant Measurement: Using Rasch Models in the Social, Behavioral, and Health Sciences, 2nd Edn. George Engelhard, Jr. & Jue Wang	Applying the Rasch Model (Winsteps, Facets) 4th Ed., Bond, Yan, Heene	Advances in Rasch Analyses in the Human Sciences (Winsteps, Facets) 1st Ed., Boone, Staver	Advances in Applications of Rasch Measurement in Science Education, X. Liu & W. J. Boone	Rasch Analysis in the Human Sciences (Winsteps) Boone, Staver, Yale
Introduction to Many-Facet Rasch Measurement (Facets), Thomas Eckes	Statistical Analyses for Language Testers (Facets), Rita Green	Invariant Measurement with Raters and Rating Scales: Rasch Models for Rater-Mediated Assessments (Facets), George Engelhard, Jr. & Stefanie Wind	Aplicação do Modelo de Rasch (Português), de Bond, Trevor G., Fox, Christine M	Appliquer le modèle de Rasch: Défis et pistes de solution (Winsteps) E. Dionne, S. Béland
Exploring Rating Scale Functioning for Survey Research (R, Facets), Stefanie Wind	Rasch Measurement: Applications, Khine	Winsteps Tutorials - free Facets Tutorials - free	Many-Facet Rasch Measurement (Facets) - free, J.M. Linacre	Fairness, Justice and Language Assessment (Winsteps, Facets), McNamara, Knoch, Fan
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Rasch Measurement Transactions & Rasch Measurement research papers - free	An Introduction to the Rasch Model with Examples in R (eRm, etc.), Debelak, Strobl, Zeigenfuse	Rasch Measurement Theory Analysis in R, Wind, Hua	Applying the Rasch Model in Social Sciences Using R, Lamprianou	El modelo métrico de Rasch: Fundamentación, implementación e interpretación de la medida en ciencias sociales (Spanish Edition), Manuel González-Montesinos M.
Rasch Models: Foundations, Recent Developments, and Applications, Fischer & Molenaar	Probabilistic Models for Some Intelligence and Attainment Tests, Georg Rasch	Rasch Models for Measurement, David Andrich	Constructing Measures, Mark Wilson	Best Test Design - free, Wright & Stone Rating Scale Analysis - free, Wright & Masters
Virtual Standard Setting: Setting Cut Scores, Charalambos Kollias	Diseño de Mejores Pruebas - free, Spanish Best Test Design	A Course in Rasch Measurement Theory, Andrich, Marais	Rasch Models in Health, Christensen, Kreiner, Mesba	Multivariate and Mixture Distribution Rasch Models, von Davier, Carstensen

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