Decreasing the options' number in multiple choice questions in the assessment of senior medical students and its effect on exam psychometrics and distractors' function

Background: Studies that have investigated the effect options' number in MCQ tests used in the assessments of senior medical students are scarce. This study aims to compare exam psychometrics between three- and five-option MCQ tests in final-year assessments.

Methods: A cluster randomized study was applied. Participants were classified into three groups, according to their academic levels. Students in each of those levels were randomized into either the three- or five-option test groups.

Results: Mean time to finish the five-option test was 45 min, versus 32 min for the three-option group. Cronbach's alpha was 0.89 for the three-option group, versus 0.81 for the five-options, p-value = 0.19. The mean difficulty index for the three-option group was 0.75, compared to 0.73 for the five-option group, p-value = 0.57. The mean discriminating index was 0.53 for the three-option group, and 0.45 for the five-options, p-value = 0.07. The frequency of non-functioning distractors was higher in the five-option test, 111 (56%), versus 39 (39%) in the three-options, with p-value < 0.01.

Conclusions: This study has shown that three-option MCQs are comparable to five-option MCQs, in terms of exam psychometrics. Three-option MCQs are superior to five-option tests regarding distractors' effectiveness and saving administrative time.