A teacher wanted to know whether it hurts or helps your exam performance if you rethink and change some answers on a multiple-choice test. Students in this study were told to review their final exams and change any answers they wanted to before turning them in. However, the students had to indicate both the original answer and the changed answer for each question. The teacher graded each exam twice, once using the set of original answers and once with the changes. Are the data sufficient to conclude that rethinking and (if necessary) changing your answers has an impact on test scores?