A study is conducted to estimate the average difference in bus ridership for a large city during the morning and afternoon rush hours. The transit authority's researcher randomly selects nine buses because of the variety of routes they represent. On a given day the number of riders on each bus is counted at 7:45 A.M. and at 4:45 P.M., with the following results.

Use the data to compute a 90% confidence interval to estimate the population average difference. Assume ridership is normallydistributed.

Bus Morning fternoon 43 51 37 24 47 41 49 32 42 47 51 49 50 46