The Advantages of Five-Option Multiple-Choice Items in Classroom Tests of Student Mastery

The effectiveness of multiple-choice (MC) items depends on the quality of the response options—particularly how well the incorrect options (“distractors”) attract students who have incomplete knowledge. It is often contended that test-writers are unable to devise more than two plausible distractors for most MC items, and that the effort needed to do so is not worthwhile in terms of the items’ psychometric qualities. To test these contentions, I analyzed students’ performance on 545 MC items across six science courses that I have taught over the past decade. Each MC item contained four distractors, and the dataset included more than 19,000 individual responses. All four distractors were deemed plausible in one-third of the items, and three distractors were plausible in another third. Each increase in plausible distractor led to an average of a 13% increase in item difficulty. Moreover, an increase in plausible distractors led to a significant increase in the discriminability of the items, with a leveling off by the fourth distractor. These results suggest that—at least for teachers writing tests to assess mastery of course content—it may be worthwhile to eschew recent skepticism and continue to attempt to write MC items with three or four distractors