When Majority Doesn't Rule: The Use of Discrimination Indices to Improve the Quality of MCQs.

This paper outlines the use of item analysis to assist examiners in evaluating the quality and validity of their MCQ exam questions. The generation of item analysis, particularly discrimination index, has long been established practice in professional testing and credentialing organisations and some disciplines in tertiary education, but its use appears to be inconsistent among Bioscience departments. We argue that generating some form of discrimination index is an essential part of the validation of exams, in particular to help identify errors in scoring, to identify potentially flawed questions, or to confirm the validity of challenging questions. We demonstrate each of these uses through examples drawn from first year Biology exams, with interpretations of the questions in the light of post-examination item analysis.