To
evaluate the ability of examinees, the item response theory (IRT)
gives us an useful information. The IRT evaluates the examinee's
ability and provides the item characteristics. Recently, we have
configured the adaptive online testing using the IRT as one of
the CBT (Computer Based Testing) methods, thereby we have
been able to obtain the examinee's ability rating in short testing
time. However, when the number of items is too small, we observed
biases of estimates for the ability parameter. In this study,
we have performed simulation studies under various conditions,
and have found the magnitude of such biases. In
addition, to circumvent the biases due to the Bayes procedure,
we have proposed a simple method to reduce the biases. |
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item
response theory, adaptive test, item selection, item bank,
ability estimate, bias |
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