An educational testing organization has prepared a new version of an aptitude test. The average score on the old version, based on the scores of hundreds of thousands of individuals who took the test, is 500. The new test is tried out on a sample of 50 students selected at random from those eligible to take the test. Their average score is 480, and their standard deviation is 80. We want to know whether the evidence suggests that the new version is harder than the old.
a. State the given problem as a hypothesis testing problem.
b. Give the test statistic you will use for this test as well as the corresponding P-value.
c. Carry out the test in (a) at the 5% level. What is your conclusion: is the new version of the test harder than the old one? Justify your answer.