1.

The two samples below are independent from Normal populations with equal variances.

Sample 1. n=40, sum of X= 3200, sum of X^2= 314000

Sample 2. n=11, sum of X= 530, sum of X^2= 50500

Construct a 90% confidence interval for the difference in population means. State the confidence interval in terms of sample 2 - sample 1

2.

The department of transportation provides the number of miles that residents of the largest metropolitan areas travel per day in a car. Suppose a random sample of 46 Buffalo residents and 30 Boston residents yielded the following results.

Buffalo n=46, xbar=22.3, s=8.6

Boston n=30, xbar=18.6, s=7.5

Construct a 99% confidence interval for the difference in true means. State the confidence interval in terms of Boston-Buffalo