The Commerce Department also has data available on number of shopping centers and retail sales for the South Central states. The data are given below:

Number of                    Retail Sales

State                Shopping Centers         ($ billion)

Kentucky                      593                   11.7

Tennessee                    1137                 19.1

Alabama                       601                   13.2

Mississippi                   418                   7.2

Arkansas                      339                   6.4

Louisiana                      676                   15.6

Oklahoma                     556                   11.4

Texas                           2824                 72.7

(a) Find the linear regression model for the South Central states.

(b) How does the equation for the South Central states compare to the one you found for the North Central states?

(c) Would you have expected them to be exactly the same? Why or why not?

(d) What similarities would you expect them to have? What differences?

(e) Combine the data from the North Central and South Central states and find the linear regression model for the combined data.

(f) Do you think that the individual models are better or worse than the combined model? On what criteria do you base your conclusion?