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A Comparison of Using the Fixed Common-Precalibrated Parameter Method and the Matched Characteristic Curve Method for Linking Multiple-Test Items

A linking design typically consists of a data collection procedure together with an item linking procedure that places item parameters calibrated from multiple test forms onto a common scale. This study considered 2 potentially useful item response theory linking designs. The first one is characterized by selecting a single set of common items across all multiple test forms, the precalibrated item parameters of which are kept fixed while the unknown parameters of the other items are being estimated. This linking design will be referred to as the fixed common-precalibrated item parameter design. However, data collected under this design could also be analyzed by the characteristic curve method, which constituted an alternative linking procedure. In this study, the relative merits of the 2 linking designs were examined with respect to their robustness against 3 manipulated conditions-namely, when the common items have imprecise estimates, when there is a noticeable difference in the average item difficulty between the common and the noncommon items, and when the examinees are heterogeneous in terms of their abilities. A parameter recovery study was conducted to achieve this purpose. The results indicated that both linking designs were capable of producing accurate linking of items and equivalent estimation of ability parameters under the 3 conditions. When the 2 designs were actually utilized in the development of an item bank, it was found that both linking designs produced quite consistent solutions despite minor differences on some item and ability estimates. Condition under which a linking design is preferred over the other is also provided in the Discussion section of this article.