47. Data on advertising expenditures and revenue (in thousands of dollars) for the Four Seasons Restaurant follow.

a. Let x equal advertising expenditures and y equal revenue. Use the method of least squares to develop a straight line approximation of the relationship between the two variables.

b. Test whether revenue and advertising expenditures are related at a .05 level of significance.

c. Prepare a residual plot of y versus . Use the result from part

(a) to obtain the values of .

d. What conclusions can you draw from residual analysis? Should this model be used, or should we look for a better one?