Consider the regression model you found for the data on the number of postal workers in a country and the amount of mail processed.
a. Make a plot of the residuals versus the values of the independent variables.
b. What does this lead you to believe about the appropriateness of the linear model?
c. Now plot the residuals versus the predicted values of y.
d. How do the two graphs compare? Why do you think this happened?
e. Make a normal probability plot of the data. Do you think the assumption of normality is reasonable?
f. Considering your answers to the parts (a) - (e) , do you think that the linear regression model is appropriate for these data. Why or why not?
Number of Staff Domestic Traffic
(Billions of pieces)
Germany 342,413 18.32
France 289,156 23.87
Italy 221,534 6.62
Britain 189,000 16.75
Spain 65,355 4.06
Sweden 52,251 4.21
The solution does a regression analysis.