This paper focuses on a discussion of how various
equating methods are affected by (1) sampling error,
(2) sample characteristics, and (3) characteristics of
anchor test items. Studies that examine the effect of
analytic techniques for smoothing or modeling marginal
and bivariate frequency distributions on the accuracy
of equipercentile equating are reviewed. A
need for simulation and empirical studies designed to
evaluate the effectiveness of analytic smoothing techniques
for recovering the underlying distribution when
sample size, test length, and distributional shape are
varied is identified. Studies that examine the question
of whether an equating transformation remains the
same regardless of the group used to define it are also
reviewed. The results of some studies suggested that
this may not be a problem for forms of a homogeneous
test constructed to be similar in all respects. Results
of other studies indicated that examinees who
take a test on different administration dates may vary
in systematic ways and thus affect equating results.
Finally, studies which examine the characteristics of
anchor test items are reviewed. It is concluded that
whenever groups differ in level and dispersion of ability,
special care must be taken to assure that the anchor
test is a miniature of the total test.
Cook, Linda L & Petersen, Nancy S. (1987). Problems related to the use of conventional and item response theory equating methods in less than optimal circumstances. Applied Psychological Measurement, 11, 225-244. doi:10.1177/014662168701100302
Cook, Linda L.; Petersen, Nancy S..
Problems related to the use of conventional and item response theory equating methods in less than optimal circumstances.
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