Two independent random samples are taken from two populations. The results of these samples are summarized in the following table.

Sample 1 Sample 2 LO3 n1 = 148 n2 = 135 x1 = 15.2 x2 = 11.3 s21

= 3.0 s22

= 2.1

a. Form a 90% confidence interval for 1m1 - m22.

b. Test H0: 1m1 - m22 = 0 against Ha: 1m1 - m22  0.

Use a = .01.

c. What sample size would be required if you wish to estimate 1m1 - m22 to within .2 with 90% confidence?

Assume that n1 = n2.