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How Well Can We Equate Test Forms That Are Constructed by Examinees?

Wainer, Howard; Wang, Xiang-Bo; Thissen, David
Publication Year:
Report Number:
ETS Research Report
Document Type:
Page Count:
Subject/Key Words:
Advanced Placement Program (AP), Chemistry Tests, Constructed Responses, Equated Scores, Testing Problems


When an exam consists, in whole or in part, of constructed response items, it is a common practice to allow the examinee to choose among a variety of questions. This procedure is usually adopted so that the limited number of items that can be completed in the allotted time does not unfairly affect the examinee. This results in the de facto administration of several different test forms, where the exact structure of any particular form is determined by the examinee. When different forms are administered, a canon of good testing practice requires that those forms be equated to adjust for differences in their difficulty. When the items are chosen by the examinee, traditional equating procedures do not strictly apply. In this paper we explore how one might equate within an IRT framework. We illustrate our procedure with data from the College Board's Advanced Placement Test in Chemistry. (25pp.)

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