Sensitivity of Equating Results to Different Sampling Strategies

Abstract

In this article, the results of equating two parallel forms of the College Board Biology Achievement Test using three different sampling strategies are discussed. New-form data were collected during a fall administration of the test, and old-form data were collected at a spring administration. The group taking the test in the spring was much more able, as measured by test score, than the group taking the test in the fall. The three sampling strategies studied were representative sampling, matched sampling, and reference or target sampling. For each sampling strategy, five equating procedures were studied: Tucker and Levine unequally reliable linear equatings, frequency estimation equipercentile and chained equipercentile curvilinear equatings, and three-parameter logistic (3PL) item response theory (IRT) true-score equating. The criterion for comparison in all cases was the results of a Tucker linear equating from a fall new-form/fall old-form representative sampling data collection design. Results of thi...