Pseudo-Equivalent Groups and Linking

Adjustment by minimum discriminant information provides an approach to linking test forms in the case of a nonequivalent groups design with no satisfactory common items. This approach employs background information on individual examinees in each administration so that weighted samples of examinees form pseudo-equivalent groups in the sense that they resemble samples from equivalent groups. Linking methods for equivalent groups are then applied to the weighted samples. To illustrate the approach, 29 administrations from a testing program are linked via the method of pseudo-equivalent groups. Because the forms used are currently linked by use of kernel equating, it is possible to compare the reasonableness of results from pseudo-equivalent groups to results from kernel equating.