In: Math
The following data represent a company's yearly sales volume and its advertising expenditure over a period of 5 years.
(Y) Sales in Advertising (X) Millions of Dollars in ($10,000)
15 32
16 33
18 35
17 34
16 36
(a) Develop a scatter diagram of sales versus advertising and explain what it shows regarding the relationship between sales and advertising.
(b) Use the method of least squares to compute an estimated regression line between sales and advertising by computing b0 and b1.
(c) If the company's advertising expenditure is $400,000, what are the predicted sales? Give the answer in dollars.
(d) What does the slope of the estimated regression line indicate?
a) Scatter plot using excel :
Select the data set (x,y) ---> Go to Insert menu --> Charts ---> Scatter
b) Equation of regression line : y = b0 + b1*x
Sums ∑x = 170 , ∑y = 82, ∑x*y = 2792, ∑x2 = 5790 and ∑y2 = 1350 , = 34 , = 16.4
Slope b1 =
=
Slope b1 = 0.4
Intercept b0 = - b1* = 16.4 - ( 0.4*34 )
Intercept b0 = 2.8
Equation of regression line : Sales (Y) = 2.8 + 0.4*advertisement (X)
c ) company's advertising expenditure is $400,000, We are given x = 40
Sales (Y) = 2.8 + 0.4*40
Sales (Y) = 18.8 or $188000
d) Interpretation of slope :
If there is increase in advertising expenditure by $1 then we expect to increase in company's yearly sales volume by $0.4