Chapter 10.8, Problem 65E

Operators of gasoline-fueled vehicles complain about the price of gasoline in gas stations. According to the American Petroleum Institute, the federal gas tax per gallon is constant (18.4¢ as of January 13, 2005), but state and local taxes vary from 7.5¢ to 32.10¢ for n = 18 key metropolitan areas around the country. The total tax per gallon for gasoline at each of these 18 locations is given next. Suppose that these measurements constitute a random sample of size 18:

1. a Is there sufficient evidence to claim that the average per gallon gas tax is less than 45¢? Use the t table in the appendix to bound the p-value associated with the test.
2. b Applet Exercise What is the exact p-value?
3. c Construct a 95% confidence interval for the average per gallon gas tax in the United States.