There is some evidence suggesting that you are likely to improve your test score if you rethink and change answers on a multiple-choice exam (Johnston, 1975). To examine this phenomenon, a teacher encouraged students to reconsider their answers before turning in exams. Students were asked to record their original answers and the changes that they made. When the exams were collected, the teacher found that 18 students improved their grades by changing answers and only 7 students had lower grades with the changes. The teacher would like to know if this is a statistically significant result.