Do students reduce study time in classes where they achieve a higher midterm score? In a Journal of Economic Education article (Winter 2005), Gregory Krohn and Catherine O'Connor studied student effort and performance in a class over a semester. In an intermediate macroeconomics course, they found that "students respond to higher midterm scores by reducing the number of hours they subsequently allocate to studying for the course."5 Suppose that a random sample of n = 8 students who performed well on the midterm exam was taken and weekly study times before and after the exam were compared. The resulting data are given in Table 10.6. Assume that the population of all possible paired differences is normally distributed.

a. Set up the null and alternative hypotheses to test whether there is a difference in the true mean study time before and after the midterm exam.

b. Below we present the MINITAB output for the µaired differences test. Use the output and critical values to test the hypotheses at the .101 .051 and .01 levels of significance. Has the true mean study time changed?

c. Use the p-value to test the hypotheses at the .101 .051 and .01 levels of significance. How much evidence is there against the null hypothesis?

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Paired T-Test and Cl: StudyBefore, StudyAfter Paired T for StudyBefore StudyAfter MeanStDev SE Mean studyBefore 8 15.6250 1.9955 0.7055 StudyAfter 8 11.5000 3.4226 1.2101 Difference 4.12500 2.99702 1.05961 95% CI for mean difference: 《1.61943, 6.63057) T-Test of mean difference 0 (vs not = 0) : T-Value = 3.89 P-value " 0.006