Lexus, Inc. In Exercise 12.77 we presented sales data for the Lexus GX, a mid-size s...

Lexus, Inc. In Exercise 12.77 we presented sales data for the Lexus GX, a mid-size sport utility vehicle (SUV) sold in North American and Eurasian markets by Lexus. The sales of the Lexus GX 470 from its inception until 2009 are given in the table:

a. Plot the data. What model would you expect to provide the best fit to the data? Write the equation of that model.

b. Use a computer software package to fit the model from part a.

c. Find the least-squares prediction equation relating the sales of the Lexus GX 470 to the year of production.

d. Does the model contribute significant information for the prediction of sales based on the year of production? Use the appropriate p-value to make your decision.

e. Find on the printout. What does this value tell you about the effectiveness of the multiple regression analysis?

Reference:

Lexus, Inc. The Lexus GX is a midsize sport utility vehicle (SUV) sold in North American and Eurasian markets by Lexus. The GX 470 was introduced in 2002 (as a 2003 model) and was later upgraded with a new off-road suspension system. The sales of the Lexus GX 470 from its inception until 2009 are given in the table:

a. Plot the data using a scatterplot. How would you describe the relationship between year and sales of the Lexus GX 470?

b. Even though the scatterplot in part a might indicate differently, assume that the relationship between year and sales is linear. Find the least-squares regression line relating the sales of the Lexus GX 470 to the year being measured.

c. Is there sufficient evidence to indicate that sales are linearly related to year? Use α = .05.

d. Examine the diagnostic plots shown below. What can you conclude about the validity of the regression assumptions?

e. Based on your conclusions in part d, is it advisable to predict the 2010 sales using the regression line from part b? Explain.