Irt-dif

From RiCkyPedia

IRT and DIF

Prepared by: Center for Health Improvement for Minority Elders (CHIME), UCLA

Item response theory (IRT) models are often used to investigate measurement invariance. Differential item functioning (DIF) is said to occur when the relationship between theta and item score is different across two or more studied populations. This is particularly important to assess when using scales to determine disparities between different groups of older adults.

• Bjorner, J. B., Kosinski, M., & Ware, J. E. (2003). Calibration of an item pool for assessing the burden of headaches: An application of item response theory to the Headache Impact Test (HIT). Quality of Life Research, 12, 913-933.

The paper demonstrates that a simulated computerized adaptive test of only 5 items reproduced very accurately scores based on all 47 items in the item pool.

• Embertson, S. E., Reise, S. P. (2000). Item Response Theory for Psychologists. Mahwah, NJ: Lawrence Erlbaum Associates.

Intermediate-level book on IRT models and methods. Includes a good discussion of DIF.

• Chang, C. H., & Reeve, B. B. (2005). Item response theory and its applications to patient-reported outcomes measurement. Evaluation and the Health Professions, 28, 264-282.

This didactic paper provides a fantastic soup to nuts overview of IRT.

• Crane, P. K., van Belle, G., & Larson, E. B. (2004). Test bias in a cognitive test: Differential item functioning in the CASL. Statistics in Medicine, 23, 241-256.

This article describes an ordinal logistic regression technique to assess DIF and illiustrates how IRT scoring diminished the impact of DIF. The advantages of the technique relative to other approaches is discussed.

• Hambleton, R. K., Swaminathan, H., & Rogers, H. J. (1991). Fundamentals of item response theory. Newbury Park, CA: Sage Publications.

This is an excellent introduction to all aspects of IRT models and methods that includes many fully worked examples. It discusses DIF testing and computerized adaptive testing.

• Hays, R.D., Morales, L.S., & Reise, S.P. (2000). Item response theory and health outcomes measurement in the 21 st Century. Medical Care, 38, II28-42.

This didactic paper illustrates the application of IRT methods to a variety of measurement issues. It covers all the basic issues in IRT measurement models.

• Lai, J. S., Teresi, J., & Gershon, R. (2005). Procedures for the analysis of differential item functioning (DIF) for small sample sizes. Evaluation and the Health Professions, 28, 283-294.

The paper examines methods of examining DIF that can be used with relatively small sample sizes (< 200 cases).

• Morales, L.S., Reise, S.P., & Hays, R.D. (2000). Evaluating the equivalence of health care ratings by whites and Hispanics. Medical Care, 38, 517-527.

Example of paper examining DIF in English and Spanish versions of a patient satisfaction scale using standard IRT methods.

• Reise, S.P., Widaman, K.F., & Pugh, R.H. (1993). Confirmatory factor analysis and item response theory: two approaches for exploring measurement invariance. Psychological Bulletin, 114, 552-66.

Didactic paper that examines DIF in English and Chinese samples using confirmatory factor analyses and IRT, drawing out similarities and differences between the two approaches. Well written and easy to understand.

• Teresi, J. A. (2001). Statistical methods of examination of differential item functioning with applications to cross-cultural measurement of functional, physical and mental health. J Mental Health and Aging,7, 31-40.

A great exposition of a variety of approaches to the assessment of DIF.

Last updated December 2005