The airline industry measures fuel efficiency by calculating how many miles one seat can travel, whether occupied or not, on one gallon of jet fuel. The following data show the fuel economy, in miles per seat, for 15 randomly selected flights on Delta and US Airways. These data can also be found in the Excel file fuel efficiency.xlsx. Assume the population variances for the fuel efficiency for these two airlines are not equal.

Delta US Airways 82.1 68.4 52.7 60.8 68.3 77.2 58.8 52.0 71.4 76.4 71.4 63.0 60.0 59.6 44.9 58.9 72.1 81.1 57.9 67.6 55.9 68.6 63.1 83.5 45.2 61.0 86.7 58.2 73.3 69.0

a. Perform a hypothesis test using a = 0.05 to determine if the average fuel efficiency differs between the two airlines.

b. Approximate the p-value using Table 5 in Appendix A and interpret the result.

c. Verify your results using PHStat or Excel.

d. Identify the p-value using Excel and interpret the result.

e. What assumptions need to be made in order to perform this procedure?

AppendixLO1