ERIC Number: ED395955
Record Type: RIE
Publication Date: 1988-Apr
Reference Count: N/A
A Comparison of Observed Score and True Score Equating Methods for Representative Samples Matched on an Anchor Test.
Lawrence, Ida M.; Dorans, Neil J.
This paper addresses the sample invariant properties of four equating methods (Tucker and Levine linear equating, equipercentile equating through an anchor test, and three-parameter item response theory equating). Data from several national administrations of the Scholastic Aptitude Test served as the source of data for the study. Equating results across two sampling conditions, "representative" sample and "matched" sample, were compared to determine which equating procedures produced the most consistent results. In the representative sample condition, equatings were based on old-form and new-form samples that differed in ability; in the matched sample condition, the old-form sample was selected to match the anchor test score distribution of the new-form sample. Results for the item response theory equating method differed for representative and matched samples, as did the equating results for the Levine and equipercentile methods. Results based on the Tucker observed score equating method were found to be essentially the same across representative and matched sample conditions. Results for the four equating methods tended to converge under the matched sample condition. The last section of this paper offers tentative explanations for the findings. An appendix contains formulas for the equating methods discussed. There are several series of unreadable numbers in the appendix. (Contains 2 figures, 3 tables, and 11 references.) (Author/SLD)
Publication Type: Reports - Evaluative
Education Level: N/A
Authoring Institution: Educational Testing Service, Princeton, NJ.
Identifiers: Anchor Tests; Equipercentile Equating; Levine Equating Method; Linear Equating Method; Scholastic Aptitude Test; Three Parameter Model; Tucker Common Item Equating Method