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.
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.
