A Comparison of the Frequency Estimation and Chained Equipercentile Methods Under the Common-Item Nonequivalent Groups Design

Abstract

This article uses simulation to compare two test equating methods under the common-item nonequivalent groups design: the frequency estimation method and the chained equipercentile method. An item response theory model is used to define the true equating criterion, simulate group differences, and generate response data. Three linear equating methods are also included for reference. The results show that when there is substantial group difference, the frequency estimation method has larger bias than the chained equipercentile method. The frequency estimation method, however, almost always has a smaller standard error of equating than the chained equipercentile method.