In order to test whether the average waiting time this year differs from last year, a sample of 20 data were collected this year with a mean of 0.74 hours and standard deviation 0.22 hours. Calculate the 99% confidence interval for the true waiting time for banking service this year.

0.22 O + 0.74 + 2.845. 20 0.22 O 0.74 + 2.861 20 O 0.74 + 1.96 0.22 V20 O 0.74 + 2.57 . 0.22 /20