A car is advertised as getting at least 31 miles per gallon in highway driving on trips of at least 100 miles. Suppose the miles per gallon obtained in 8 independent experiments (each consisting of a nonstop highway trip of 100 miles) are
28, 29, 31, 27, 30, 35, 25, 29
(a) If we want to check if these data disprove the advertising claim, what should we take as the null hypothesis?
(b) What is the alternative hypothesis?
(c) Is the claim disproved at the 5 percent level of significance?
(d) What about at the 1 percent level?