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 9 students in the first section with 9 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 student in the change section who also had an 89 on the midterm. The final exam grades for the 9 matched pairs of students are presented in the following table.
a. Do the data indicate a significant difference between the two conditions? Use a two tailed test with α = .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.

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Matched No-Change Section Change Section Pair #1 71 86 #2 68 80 #3 91 88 # 4 65 74 #5 73 82 #6 81 89 #7 85 85 #8 86 88 #9 65 76