ERIC Number: ED375152
Record Type: Non-Journal
Publication Date: 1992-May
Reference Count: N/A
Direct and Indirect Equating: A Comparison of Four Methods Using the Rasch Model.
Morrison, Carol A.; Fitzpatrick, Steven J.
An attempt was made to determine which item response theory (IRT) equating method results in the least amount of equating error or "scale drift" when equating scores across one or more test forms. An internal anchor test design was employed with five different test forms, each consisting of 30 items, 10 in common with the base test and 5 to 10 in common with one or more other forms. Simulated data were generated for each using the Rasch model. Using one form as the base test, each of the others was equated directly to the base test and equated through one or more others to the base test. Equating methods examined were: (1) concurrent calibration; (2) equating constant procedure; (3) major axis procedure; and (4) fixed bs procedure. When equating error was assessed, it was found that concurrent calibration resulted in the least amount of equating error overall. When concurrent calibration is not feasible, results indicate that major axis equating results in the least amount of equating error when equating across one or more forms. (Contains 5 references, 6 tables, and 1 figure.) (Author/SLD)
Publication Type: Reports - Research
Education Level: N/A
Authoring Institution: Texas Univ., Austin. Measurement and Evaluation Center.