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
		= 72 (in $1,000)	= 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.