Local Equating of Cognitively Diagnostic Modeled Observed Scores

A local equating method of cognitively diagnostic modeled observed score was introduced to address the problem of equating without anchor test as well as the satisfaction of equating criteria. The criterion of test construct was redefined on attribute level. Then, a true family of equating transformations given attribute mastery pattern was derived from the criterion of equity, which is the main concern of local equating. The results of simulation studies showed a substantial bias for the traditional equipercentile equating under the equivalent groups design but much smaller bias for the local method. The proposed method also showed satisfactory performances under the nonequivalent groups design even without anchor test. The local method appeared to be quite robust with respect to changes in the sample size, but its biases became larger with increasing model misfit.