模式錯誤假設對電腦化測驗的影響

The Effect of Model Misspecification on Computerized Testing

試題反應理論被廣泛地使用在電腦化適性測驗上，其以機率的觀點，透過試題反應模式，解釋考生能力與試題間的關係。藉由所選擇的試題反應模式，施測者可以根據不同的測驗目的編製適合的測驗。然而在實際的測驗情境中，試題反應模式通常是未知且須事先認定的。本研究旨在探討試題反應模式錯誤假設對測驗結果造成之影響，研究結果顯示，在常模參照測驗中，試題反應模式錯誤假設對考生能力估計所產生的偏誤比在真實模式下來的大，並造成測驗成本的增加，尤以真實測驗模式為3PLM 時最為嚴重。在效標參照測驗中，試題反應模式錯誤假設對分類結果影響不大，但會造成測驗題數的增加，浪費施測成本。

Item response theory (IRT) has been widely applied in computerized adaptive testing (CAT) with the logistic type models most often used. IRT prescribes an item characteristic curve that provides the probability of an examinee correctly answering an item with a parameter of a given ability level. Examiners can develop various tests for different purposes based on a chosen item response model. However， in actual testing practice， the priori item response model is often unknown. The purpose of this study is to examine the effect of model misspecification on computerized testing. Using norm-referenced testing， results indicated that model misspecification has an effect on the estimate of examinees' abilities. Both the RMSE and test length significantly increased when the wrong item response models were used， especially when item bank belongs to three-parameter logistic model. In criterion-referenced testing， model misspecification has no effect on the accuracy of classification. However， it will increase test length and cost of testing.