Should students change their answers on multiple choice questions?

Multiple choice exams are ubiquitous, but advice on test-taking strategies varies and is not always well informed by research. This study evaluated the question of whether students benefit or are harmed when they change their initial answers on multiple choice questions in the context of physiology and biology courses. Previously marked examinations were reviewed for eraser marks that indicated answer changes, and the impact of these changes on exam grades was tabulated. In addition, faculty and students were surveyed for their opinions about changing answers. A plurality of faculty (36%) reported a belief that answer changes usually harm student grades, whereas a slim majority of students (51%) believed that answer changing helped their scores (χ 2  = 60.52, P < 0.0001). Empirically, across two exams, students changed their answer from an incorrect answer to a correct one 2.8 times (SD 2.2) compared with 1.0 time (SD 1.4) changing in the negative direction. Therefore, on average, students benefited ( V =  123.5, P < 0.0001) from answer changing. Furthermore, comparing across two exams in the same course, some students were consistently more likely to change their answers than others (adjusted R 2 = 0.23, P < 0.0001), but the impact of changing answers on the first exam provided no prediction of how much a student would benefit from answer changing on the second exam (adjusted R 2 = −0.004, P = 0.42). These data support the argument that students should be advised to review and revise responses to exam questions before submitting them.