Looking for a great airfare? Consumer Reports has several hints about how to minimize your costs, which include being flexible about travel dates and times, checking multiple websites, and knowing when to book your flight. One suggestion involved checking fares at "secondary" airports-airports that might be slightly farther from your home, but where fares are lower. For example, the average of all domestic ticket prices at Los Angeles International Airport (LAX) was quoted as $349 compared to an average price of $287 at nearby Ontario International Airport (ONT). Suppose that these estimates were based on random samples of 1000 domestic tickets at each airport and that the standard deviation of the prices at both airports was $200.
a. Is there sufficient evidence to indicate that the mean ticket prices differ for these two airports at the α = .05 level of significance? Use the large-sample z-test. What is the p-value of this test?
b. Construct a 95% confidence interval for (µ1 - µ2). Does this interval confirm your conclusions in part a?