Chapter 15, Problem 6PS

An automotive sales manager wishes to examine the relationship between age (years) and sales price $\left(\text{\$}\right)$ for used Honda automobiles. The file HondaPrices contains data for a sample of Honda Civic LXs that were listed for sale at a car shopping website.

a. Construct a scatter plot for age and price.

b. Fit a quadratic regression model to predict price and state the quadratic regression equation.

c. Predict the mean price of a Honda Civic LX that is five years old.

d. Perform a residual analysis on the result and determine whether the regression model is

valid.

e. At the 0.05 level of significance, is there a significant quadratic relationship between age and price?

f. What is the p-value in (e)? interpret its meaning.

g. At the 0.05 level of significance, determine whether the quadratic model is a better fit than the linear model.

h. What is the p-value (g)? Interpret its meaning.

i. interpret the meaning of the coefficient of multiple determination.

j. Compute the adjusted ${\text{r}}^{\text{2}}.$

k. What conclusions can you reach concerning the relationship between age and price?