Below are fitted regressions based on used vehicle ads. Observed ranges of X are shown. The assumed regression model is AskingPrice = f (VehicleAge).
(a) Interpret the slopes.
(b) Are the intercepts meaningful? Explain.
(c) Assess the fit of each model.
(d) Is a bivariate model adequate to explain vehicle prices?
If not, what other predictors might be considered? (Data are from Detroit's AutoFocus 4, Issue 38 [September 17-23, 2004]. Data are for educational purposes only and should not be viewed as a guide to vehicle prices.)
|
Vehicle
|
n
|
Intercept
|
Slope
|
R2
|
Min Age
|
Max Age
|
|
Ford Explorer
|
31
|
22,252
|
-2,452
|
.643
|
2
|
6
|
|
Ford F-150 Pickup
|
43
|
26,164
|
-2,239
|
.713
|
1
|
37
|
|
Ford Mustang
|
33
|
21,308
|
-1,691
|
.328
|
1
|
10
|
|
Ford Taurus
|
32
|
13,160
|
-906
|
.679
|
1
|
14
|