The Federal Aviation Administration (FAA) increased the frequency and thoroughness of its review of aircraft maintenance procedures in response to the admission by ValuJet Airlines that it had not met some maintenance requirements. Suppose that the FAA samples the records of six aircraft currently utilized by one airline and determines the number of flights between the last two complete engine maintenances for cach, with the results shown in the table. The FAA requires that this maintenance be performed at least every 30 flights. Although it is obvious that not all aircraft are meeting the requirement, the FAA wishes to test whether the airline is meeting this particular maintenance requirement "on average."

a. Would you suggest the t-test or sign test to conduct the test? Why?

b. Set up the nil1 and alternative hypotheses such that the burden of proof is on the airline to show it is meeting the "on-average" requirement.

c. What are thc test statistic and rejection region for this test if the level of significance is a = .01? Why would the level of significance be set at such a low value?

d. Conduct the test, and state the conclusion in terms of this application.