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ERIC Number: ED409334
Record Type: Non-Journal
Publication Date: 1997-Mar
Pages: 44
Abstractor: N/A
Reference Count: N/A
The Effects of Content Mix and Equating Method on the Accuracy of Test Equating Using Anchor-Item Design.
Yang, Wen-Ling
Using an anchor-item design of test equating, the effects of three equating methods (Tucker linear and two three-parameter item-response-theory-based (3PL-IRT) methods), and the content representativeness of anchor items on the accuracy of equating were examined; and an innovative way of evaluating equating accuracy appropriate for the particular item-sampling design of the study was introduced. Data analyzed were test results from 2 forms of a professional competency examination with 197 and 203 items respectively. There were 145 anchor items embedded in both forms, and the 2 examinee groups were not randomly formed. From the two test forms, four pairs of shortened test forms were created to differ in the content representativeness of their anchor items. The total raw score on the original anchor items was regarded as a "pseudo true score," which was used as a criterion for evaluating equating accuracy. Overall, the three equating methods appeared to yield moderately accurate equating results on every test, but the outcomes of the IRT-based methods seemed to be more accurate than the outcomes of the Tucker method. The accuracy of equating depended on the content representativeness of the anchor items, no matter which method was used to equate test forms. The 3PL-IRT model seemed appropriate for equating the test form with negative skewed score distribution. One appendix presents the item sampling schemes and the other contains tables of correlation analyses on anchor and nonanchor items. (Contains 6 tables, 2 figures, and 58 references.) (SLD)
Publication Type: Reports - Evaluative; Speeches/Meeting Papers
Education Level: N/A
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A