Practical Consequences of Chained Equating

In the present study, a common examinee design was used to verify the equating error and practical consequences of the chained equating method, from the viewpoint of model misfit. The factors of model misfit that were selected were (a) the non-normality of the ability distribution of common examinees, and (b) differential item functioning (DIF). The independent variables were the change in the ability distribution of the common examinees, the number of equating chains, and the type and degree of differential item functioning. The evaluation criteria were the bias and standard error of the estimated scaled scores and the accuracy of classifying the examinees into 4 categories. A simulation study examined influences of the 3 independent variables. The results indicated the following: (a) 99 % of the variance of the estimated scaled scores was random error, (b) using a DTM (difference that matters) criterion, the 3 factors did not cause a bias that was problematic in practice, (c) the number of chains had the greatest influence on the standard error, so that if the number of chains was 4 or more, a standard error exceeding the DTM criterion was likely to occur, and (d) the accuracy of classifying the examinees into the 4 categories was hardly affected by the 3 factors.