(b)

To estimate the length of delays in flights, the airline has randomly sampled 80

of its flights. The observed sample mean is 15.5 minutes of delay per flight, and

the observed sample standard deviation is 6.7 minutes. Construct a 95% confi-

dence interval for the mean delay per flight.

(c)

How many flights should the airline sample in order to estimate the mean delay

per flight to within 1 minute at the 99% confidence level?

(d)

A very important statistic in understanding customer satisfaction in the airline

industry is the fraction of flights that arrive on time. In the sample of 80 flights

(part (b)), 60 flights arrived on time, while 20 experienced some delay. Construct

a 95% confidence interval for the proportion of flights that arrive on time.

(e)

How many flights should the airline sample in order to predict the proportion of

flights that arrive on time to within 2%, at the 95% confidence level?

All part of the same 4.18 main question