In order to estimate 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
x1 =72 (in $1,000) x2 =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 ? = 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.