Chapter 11.10, Problem 69E

The manufacturer of Lexus automobiles has steadily increased sales since the 1989 launch of that brand in the United States. However, the rate of increase changed in 1996 when Lexus introduced a line of trucks. The sales of Lexus vehicles from 1996 to 2003 are shown in the accompanying table.¹⁰

1. a Letting Y denote sales and x denote the coded year (–7 for 1996, –5 for 1997, through 7 for 2003), fit the model $Y={\beta }_0+{\beta }_{1}x+\epsilon$.
2. b For the same data, fit the model $Y={\beta }_0+{\beta }_{1}x+{\beta }_2{x}^2+\epsilon$.