Correcting for guessing increases validity in multiple-choice examinations in an oral and maxillofacial pathology course.

A standard correction for random guessing on multiple-choice examinations was examined retrospectively in an oral and maxillofacial pathology course for second-year dental students. The correction was a weighting formula for points awarded for correct answers, incorrect answers, and unanswered questions such that the expected value of the increase in test score due to guessing was zero. We compared uncorrected and corrected scores on examinations using a multiple-choice format with scores on examinations composed of short-answer questions. The short-answer format eliminated or at least greatly reduced the potential for guessing the correct answer. Agreement of corrected multiple-choice scores with short-answer scores (intraclass correlation coefficient 0.78) was significantly (p=0.015) higher than agreement of uncorrected multiple-choice scores with short-answer scores (intraclass correlation coefficient 0.71). The higher agreement indicated increased validity for the corrected multiple-choice examination.