d. What is your statistical decision? 3. To test the effectiveness of a business school preparation course, 10 students took a general business test before and after the course. The results are given below. Exam Score After the Course Exam Score Before the Course 640 790 a. Use an appropriate hypothesis test, at 0.05 level of signicance, to determine whether there is evidence of a difference between before and after scores of the students. b. What assumption is necessary to perform the hypothesis test in (a)? c. Construct a 95% confidence interval estimate of the mean difference in before and after scores. Interpret the interval. What is your decision based on this confidence interval estimate? 4. The following information is available for two samples selected from independent normally distributed populations