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 gave the same final exam to two sections of a psychology course. The students in one section were told to turn in their exams immediately after finishing, without changing any of their answers. In the other section, students were encouraged to reconsider each question and to change answers whenever they felt it was appropriate. Before the final exam, the teacher had matched nine students in the first section with nine students in the second section based on their midterm grades. For example, a student in the no-change section with an 89 on the midterm exam was matched with a student in the change section who also had an 89 on the midterm. The difference between the two final exam grades for each matched pair was computed, and the data showed that the students who were allowed to change answers scored higher by an average of MD 5 7 points with SS 5 288.
a. Do the data indicate a significant difference between the two conditions? Use a two-tailed test with a 5 .05.
b. Construct a 95% confidence interval to estimate the size of the population mean difference.
c. Write a sentence demonstrating how the results of the hypothesis test and the confidence interval would appear in a research report
