Many students regularly complain that the cost of college textbooks is constantly increasing. However, the National Association of College Stores released data for 2016 and 2017 for the average amount of money spent on course materials, which shows that the average in 2016 was $327 and in 2017 $252. Your college wants to perform its own study and selected a random sample of students in 2017 and again in 2018. The amount of money each student spent in stores and on Web sites on course materials was recorded. These data can be found in the Excel file course materials.xlsx. Assume that the population variances for the amounts spent during these two years are equal.

a. Using a = 0.10, perform a hypothesis test to determine if the average amounts spent on course materials during these two years differs.

b. Construct a 90% confidence interval to estimate the average difference in the amounts spent by students between the two years. Interpret your result.

c. Identify the p-value and interpret the result.

d. What assumptions need to be made in order to perform this procedure?