Abstract
The need for equating arises when two or more tests on the same construct or subject area can yield different scores for the same examinee. The goal of test equating is to allow the scores on different forms of the same tests to be used and interpreted interchangeably. Item response theory (IRT; Hambleton, Swaminathan, & Rogers, 1991; Lord, 1980; Thissen & Wainer, 2001) has provided new ways to approach test equating. Using IRT in the equating process usually also requires some sort of linking procedure to place the IRT parameter estimates on a common scale
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Notes
- 1.
The mdltm software is a command line controlled program that runs on various operating systems. Executables can be made available for noncommercial purposes upon request; please contact the first author of this chapter for details.
- 2.
A more general result holds: All strictly monotone transformations of θ are also permissible. This feature, however, will not be pursued further in this chapter.
- 3.
An alternative to procedures relying on these averages is to remove the indeterminacy by setting one item difficulty and the slope of that item to prespecified constants, and fix these values for that item without updating in the maximization.
- 4.
The polytomous items are not shown in the tables but were part of the data, with mixed item format in both calibrations.
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von Davier, M., von Davier, A.A. (2009). A General Model for IRT Scale Linking and Scale Transformations. In: von Davier, A. (eds) Statistical Models for Test Equating, Scaling, and Linking. Statistics for Social and Behavioral Sciences. Springer, New York, NY. https://doi.org/10.1007/978-0-387-98138-3_14
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