Test publishers generally choose an anchor or scaling
test approach to the development of a growth scale
for a multilevel achievement battery. Although some
studies have been conducted comparing traditional
equipercentile equating procedures with item response
theory models using the anchor test (overlapping
items) approach, to date there is no evidence on the
comparability of equating procedures when the scaling
test approach is used. The purpose of this study was
to compare the equipercentile, Rasch, one-parameter
modified logistic, and two-parameter logistic item response
theory procedures in the equating of a multilevel
achievement test battery using the scaling test
approach. Since the equipercentile method has been
widely used by test publishers, it was chosen as a
standard for comparison of the experimental results.
Individual item pseudo-guessing parameters were
specified for the one-parameter modified logistic and
two-parameter logistic item response theory models
based on the proportion of students in the national
standardization sample selecting the least attractive
distractor for the item. Two grades—fourth and
eighth—and two subtests—reading and mathematics—
were selected for analysis. The results of the study
suggest that for a small-sample situation in which the
scaling test approach has been applied to a multilevel
achievement battery, the one-parameter modified and
two-parameter item response theory methods (as modified
in this study) appear to be viable alternatives to
the equipercentile procedure.
Phillips, S. E. (1983). Comparison of equipercentile and item response theory equating when the scaling test method is applied to a multilevel achievement battery. Applied Psychological Measurement, 7, 267-281. doi:10.1177/014662168300700303
Phillips, S. E..
Comparison of equipercentile and item response theory equating when the scaling test method is applied to a multilevel achievement battery.
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