Lexus, Inc. The Lexus GX is a midsizesport utility vehicle (SUV) sold in NorthAmerican

Chapter 12, Problem 77

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Lexus, Inc. The Lexus GX is a midsizesport utility vehicle (SUV) sold in NorthAmerican and Eurasian markets by Lexus. The GX470 was introduced in 2002 (as a 2003 model) and waslater upgraded with a new off-road suspension system.The sales of the Lexus GX 470 from its inception until2009 are given in the table:18Generation Model(s) Calendar Year Total Sales (U.S.)2002 2,1902003 31,3762004 35,420UZJ120 GX 470 2005 34,3392006 25,4542007 23,0352008 15,7592009 6,235a. Plot the data using a scatterplot. How would youdescribe the relationship between year and salesof the Lexus GX 470? b. Even though the scatterplot in part a might indicatedifferently, assume that the relationship betweenyear and sales is linear. Find theleast-squares regression line relating the sales ofthe Lexus GX 470 to the year being measured.c. Is there sufficient evidence to indicate that salesare linearly related to year? Use a .05.d. Examine the diagnostic plots shown below.What can you conclude about the validity of theregression assumptions? e. Based on your conclusions in part d, is it advisableto predict the 2010 sales using the regressionline from part b? Explain