IRT Differential Item Functioning: An Examination of Ability Scale Purifications

Abstract

Item Response Theory (IRT) differential item functioning (DIF) methods were employed to determine the accuracy of item classification as biased or unbiased. The procedure involved a combination of Drasgow's iterative item parameter linking method and Lord's ability scale purification procedure. Biased items were created using a two-dimensional noncompensatory IRT model. Previous research had demonstrated that the iterative linking and ability scale purification (ILAP) method held promise for discerning biased from unbiased items in one simulated unidirectional DIF condition. The present study found that ILAP was at times more effective than iterative linking alone primarily by reducing false negatives and occasionally reducing false positive misidentifications. The choice of significance level employed for detection of DIF did influence the convergence of the ILAP method. The method does hold some promise for improving correct classification of test items as biased or unbiased.

Get full access to this article

View all access options for this article.

References

Ansley, T. N. , & Forsyth, R. A. (1985). An examination of the characteristics of unidimensional IRT parameter estimates derived from two-dimensional data. Applied Psychological Measurement, 9, 37-48.

Berk, R. A. (1982). Introduction. In R. A. Berk (Ed.), Handbook of methods for detecting test bias. Baltimore, MD: Johns Hopkins University Press.

Candell, G. L. , & Drasgow, F. (1988). An iterative procedure for linking metrics and assessing item bias in item response theory. Applied Psychological Measurement, 12, 253-260.

Crocker, L. , & Algina, J. (1986). Introduction to classical and modern test theory. New York: CBS College Publishing.

Divgi, D. R. (1985). A minimum chi-square method for a common metric in item response theory. Applied Psychological Measurement, 9, 413-415.

Donlon, T. F. (1984). The College Board technical handbook for the Scholastic Aptitude Test and Achievement Tests. New York: College Entrance Examination Board.

Drasgow, F. (1984). Scrutinizing psychological tests: Measurement equivalence and equivalent relations with external variables are the central issues. Psychological Bulletin, 95, 134-135.

Drasgow, F. (1987). Study of measurement bias of two standardized psychological tests. Journal of Applied Psychology, 72, 19-29.

Hambleton, R. K. , & Swaminathan H. (1985). Item response theory: Principles and applications. Hingham, MA: Kluwer-Nijhoff.

10.

Lautenschlager, G. J. , & Park, D. G. (1988). IRT item bias detection procedures: Issues of model misspecification, robustness, and parameter linking. Applied Psychological Measurement, 12, 365-376.

11.

Linn, R. L. , Levine, M. V. , Hastings, C. N. , & Wardrop, J. L. (1981). Item bias in a testof reading comprehesion. Applied Psychological Measurement, 5, 159-163.

12.

Lord, F. M. (1980). Applications of item response theory to practical testing problems. Hillsdale, NJ: Lawrence Erlbaum.

13.

McCauley, C. D. , & Mendoza, J. L. (1985). A simulation study of item bias using a two-parameter item response model. Applied Psychological Measurement, 9, 389-400.

14.

McLaughlin, M. E. , & Drasgow, F. (1987). Lord's chi-square test of item bias with estimated and with known person parameters. Applied Psychological Measurement, 11, 161-174.

15.

Park, D. G. (1988). Investigations of item response theory item bias detection. Unpublished doctoral dissertation, University of Georgia, Department of Psychology.

16.

Park, D. G. , & Lautenschlager, G. J. (1990). Iterative linking and ability scale purification as means for improving IRT item bias detection. Applied Psychological Measurement, 14, 163-173.

17.

Shepard, L. A. , Camilli, G. , & Williams, D. M. (1984). Accounting for statistical artifacts in item bias research. Journal of Educational Statistics, 22, 77-105.

18.

Shepard, L. A. , Camilli, G. , & Williams, D. M. (1985). Validity of approximation techniques for detecting item bias. Journal of Educational Measurement, 22, 77-105.

19.

Stocking, M. L. , & Lord, F. M. (1983). Developing a common metric in item response theory. Applied Psychological Measurement, 7, 201-210.

20.

Swaminathan, H. , & Gifford, J. A. (1980) Estimation of parameters in the three parameter latent trait model (Laboratory of Psychometric and Evaluation Research Rep. No. 90). Amherst: University of Massachusetts, School of Education.

21.

Sympson, J. B. (1978). A model for testing with multidimensional items. In D. J. Weiss (Ed.), Proceedings of the 1977 Computerized Adaptive Testing Conference (pp. 82-98). Minneapolis: University of Minnesota, Department of Psychology, Psychometric Methods Program.

22.

Wingersky, M. S. , Barton, M. A. , & Lord, F. M. (1982). LOGIST user s guide. Princeton, NJ: Educational Testing Service.