Chicago O’Hare and Atlanta Hartsfield-Jackson are the two busiest airports in the United States. The congestion often leads to delayed flight arrivals as well as delayed flight departures. The Bureau of Transportation tracks the on-time and delayed performance at major airports (Travel & Leisure, November 2006). A flight is considered delayed if it is more than 15 minutes behind schedule. The following sample data show the delayed departures at Chicago O’Hare and Atlanta Hartsfield-Jackson airports.

434 Chapter 10 Inference About Means and Proportions with Two Populations Chicago O’Hare Atlanta Hartsfield-Jackson Flights 900 1200 Delayed Departures 252 312

a. State the hypotheses that can be used to determine whether the population proportions of delayed departures differ at these two airports.

b. What is the point estimate of the proportion of flights that have delayed departures at Chicago O’Hare?

c. What is the point estimate of the proportion of flights that have delayed departures at Atlanta Hartsfield-Jackson?

d. What is the p-value for the hypothesis test? What is your conclusion?