Refer to the Grinfield Service Company discussed in Exercise 14-69.

a. Develop the least squares regression equation for these variables. Plot the regression line on the scatter plot.

b. Develop a 95% confidence interval estimate for the increase in sales resulting from increasing the advertising budget by $50. Interpret the interval.

c. Discuss whether it is appropriate to interpret the intercept value in this model. Under what conditions is it appropriate? Discuss.

d. Develop a 90% confidence interval for the mean sales amount achieved during all weeks in which advertising is $200 for the week.

e. Suppose you are asked to use this regression model to predict the weekly sales when advertising is set at

$100. What would you reply to the request?

Discuss.