Delta has a new jumbo jet they believe will decrease the flight time from Newark to LondonHeathrow. To be faster than its competitors, the mean must be less than 6 h 50 minutes (or 410 minutes). Because of costs, the agency monitoring the flight times only requires that eight trials be run. The results (in minutes) are given in the spreadsheet.

If the FAA requires that the agency be 90% confident of its findings (so an alpha level of 0.10), what should the agency report? Conduct an appropriate hypothesis test using Excel. Assume the population distribution is approximately normal.

find a 80% confidence interval using Excel and verify that your conclusion is the same as that of your test. We would use 80%, rather than 90% since our test claimed alpha was all in one tail (a one-tailed test). Our interval must use the same level of significance in two tails.