Travel and Transportation
Airline travelers are often plagued by long delays on the tarmac waiting to take off. In April 2013 there were six flights in the United States with tarmac times of more than 3 hours; four were international flights.40 A random sample of 25 planes at the Charlotte Douglas International Airport was obtained, and the tarmac time (in minutes) was recorded for each. The sample variance was 181.55.
a. Find a 95% confidence interval for the population variance in tarmac times. Assume normality.
b. Airlines would like to reduce tarmac times, of course, and lower the variance. Is there any evidence to suggest that the population variance is less than 100 minutes? Justify your answer.