Is It Necessary to Make Anchor Tests Mini‐Versions of the Tests Being Equated or Can Some Restrictions Be Relaxed? |
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| Authors: | Sandip Sinharay Paul W Holland |
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| Institution: | ETS, Princeton, NJ |
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| Abstract: | It is a widely held belief that anchor tests should be miniature versions (i.e., minitests), with respect to content and statistical characteristics, of the tests being equated. This article examines the foundations for this belief regarding statistical characteristics. It examines the requirement of statistical representativeness of anchor tests that are content representative. The equating performance of several types of anchor tests, including those having statistical characteristics that differ from those of the tests being equated, is examined through several simulation studies and a real data example. Anchor tests with a spread of item difficulties less than that of a total test seem to perform as well as a minitest with respect to equating bias and equating standard error. Hence, the results demonstrate that requiring an anchor test to mimic the statistical characteristics of the total test may be too restrictive and need not be optimal. As a side benefit, this article also provides a comparison of the equating performance of post-stratification equating and chain equipercentile equating. |
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