Question

If the average commute time is 10.9 miles, but the average is actually the mean of a sample of 300 commuters and the sample standard deviation is 6.2 miles Estimate the true mean commute distance using 99% confidence level.
Kuai

10.9 - +2.575 *6.2/√300

10-+ 0.9217

= (9.98, 11.82)