Test Score Equating Using a Mini-Version Anchor and a Midi Anchor: A Case Study Using SAT® Data

• Published in: Journal of educational measurement 2011-12, Vol.48 (4), p.361-379
• Main Authors: Liu, Jinghua, Sinharay, Sandip, Holland, Paul W., Curley, Edward, Feigenbaum, Miriam
• Format: Article
• Language: English
• Subjects: Ability differences; Accuracy; Bias; Case Studies; College Entrance Examinations; Cost containment; Difficulty Level; Educational evaluation; Educational testing; Educational tests & measurements; Equated Scores; Estimation bias; Item difficulty; Item response theory; Mathematical functions; Netherlands; Sampling bias; SAT (College Admission Test); Standard deviation; Standardized tests; Synthetic populations; Test Items; Test scores; Testing Programs
• ISSN: 0022-0655; 1745-3984
• DOI: 10.1111/j.1745-3984.2011.00150.x

This study explores an anchor that is different from the traditional miniature anchor in test score equating. In contrast to a traditional "mini"anchor that has the same spread of item difficulties as the tests to be equated, the studied anchor, referred to as a "midi" anchor (Sinharay & Holland), has a smaller spread of item difficulties than the tests to be equated. Both anchors were administered in an operational SAT administration and the impact of anchor type on equating was evaluated with respect to systematic error or equating bias. Contradicting the popular belief that the mini anchor is best, the results showed that the mini anchor does not always produce more accurate equating functions than the midi anchor; the midi anchor was found to perform as well as or even better than the mini anchor. Because testing programs usually have more middle difficulty items and few very hard or very easy items, midi external anchors are operationally easier to build. Therefore, the results of our study provide evidence in favor of the midi anchor, the use of which will lead to cost saving with no reduction in equating quality.