Question: In order to estimate the difference between the yearly incomes of marketing

managers in the East and West of the United States, the following information was gathered.

East West

n1?? 40 n2?? 45

×?1?? 72 (in $1,000) ?×?2? 78 (in $1,000)

s1?? 6 (in $1,000) s2?? 8 (in $1,000)

a. Develop an interval estimate for the difference between the average yearly incomes

of the marketing managers in the East and West. Use?a = 0.05.

b. At 95% confidence, use the p-value approach and test to determine if the average

yearly income of marketing managers in the East is significantly different from the West.