A travel company is investigating whether the average cost of a hotel stay in a certain city has increased over the past year. The company recorded the cost of a one-night stay for a Friday night in January of the current year and in the previous year for 31 hotels selected at random. The difference in cost (current year minus previous year) was calculated for each hotel. Which of the following is the appropriate test for the companyâs investigation?
A. A one-sample zz-test for a population mean A
B. A one-sample tt-test for a sample mean B
C. A one-sample zz-test for a population proportion C
D. A matched-pairs tt-test for a mean difference D
E. A two-sample tt-test for a difference between means E