Two procedures, one based on item difficulties, the other based on person abilities, were used to equate 14 forms of a reading comprehension test using the Rasch model. These forms had no items in common. For practical purposes, the two procedures produced equivalent results. An advantage of common-person equating for testing the unidimensionality assumption is pointed out, and the need for caution in interpreting tests of common-item invariance is stressed.
Get full access to this article
View all access options for this article.
References
1.
Angoff, W.H. (1971). Scales, norms, and equivalent scores. In R. L. Thorndike (Ed.), Educational measurement (2nd ed., pp. 508-600). Washington DC: American Council on Education.
2.
Divgi, D.R. (1981). Model-free evaluation of equating and scaling . Applied Psychological Measurement, 5, 203-208.
3.
Education Department of Western Australia. ( 1983). The Tests of Reading Comprehension: Users' guide. Perth, Western Australia: Author.
4.
Guskey, T.R. (1981). Comparison of a Rasch model scale and the grade-equivalent scale for vertical equating of test scores. Applied Psychological Measurement, 5, 187-201.
5.
Holmes, S.E. (1982). Unidimensionality and vertical equating with the Rasch model. Journal of Educational Measurement, 19, 139-147.
6.
Lord, F.M. (1975). A survey of equating methods based on item characteristic curve theory (ETS RB 75-13). Princeton NJ: Educational Testing Service.
7.
Loyd, B.H., & Hoover, H.D. (1950). Vertical equating using the Rasch model. Journal of Educational Measurement, 17, 179-193.
8.
Molenaar, I.W. (1983). Some improved diagnostics for failure of the Rasch model. Psychometrika, 48, 49-72.
9.
Slinde, J.A., & Linn, R.L. (1978). An exploration of the adequacy of the Rasch model for the problem of vertical equating. Journal of Educational Measurement, 15, 23-35.
10.
Slinde, J.A., & Linn, R.L. (1979a). A note on vertical equating via the Rasch model for groups of quite different ability and tests of quite different difficulty . Journal of Educational Measurement, 16, 159-165.
11.
Slinde, J.A., & Linn, R.L. (1979b). The Rasch model, objective measurement, equating and robustness. Applied Psychological Measurement, 3, 437-452.
12.
van den Wollenberg, A.L. (1982). A simple and effective method to test the dimensionality axiom of the Rasch model. Applied Psychological Measurement , 6, 83-91.
13.
Wright, B.D. (1977). Solving measurement problems with the Rasch model . Journal of Educational Measurement, 14, 97-116.
