1. A regional planner is studying the demographics in a region of a particular state. She has gathered the following data on nine counties.
|
County
|
Median Income
|
Median Age
|
Coastal
|
|
A
|
$48,157
|
57.7
|
1
|
|
B
|
48,568
|
60.7
|
1
|
|
C
|
46,816
|
47.9
|
1
|
|
D
|
34,876
|
38.4
|
0
|
|
E
|
35,478
|
42.8
|
0
|
|
F
|
34,465
|
35.4
|
0
|
|
G
|
35,026
|
39.5
|
0
|
|
H
|
38,599
|
65.6
|
0
|
|
J
|
33,315
|
27.0
|
0
|
a. Is there a linear relationship between the median income and median age?
b. Which variable is the "dependent" variable?
c. Use statistical software to determine the regression equation. Interpret the value of the slope in a simple regression equation.
d. Include the aspect that the county is "coastal" or not in a multiple linear regression analysis using a "dummy" variable. Does it appear to be a significant influence on incomes?
e. Test each of the individual coefficients to see if they are significant.
f. Make a plot of the residuals and comment on whether they appear to follow a nor- mal distribution.
g. Plot the residuals versus the fitted values. Do they seem to have the same amount of variation?