problem-10.27

problem-10.27  Only the Weight variable is selected.
> library(MASS)                 # load data set
> res = lm(MPG.city ~ EngineSize + Weight + Passengers + Price, data=Cars93)
> summary(res)

Call:
lm(formula = MPG.city ~ EngineSize + Weight + Passengers + Price,
    data = Cars93)

Residuals:
    Min      1Q  Median      3Q     Max
-6.1207 -1.9098  0.0522  1.1294 13.9580

Coefficients:
            Estimate Std. Error t value Pr(>|t|)
(Intercept) 46.38941    2.09752   22.12  < 2e-16 ***
EngineSize   0.19612    0.58888    0.33     0.74
Weight      -0.00821    0.00134   -6.11  2.6e-08 ***
Passengers   0.26962    0.42495    0.63     0.53
Price       -0.03580    0.04918   -0.73     0.47
---
Signif. codes:  0 `***' 0.001 `**' 0.01 `*' 0.05 `.' 0.1 ` ' 1
...
> stepAIC(res)
Start:  AIC= 212.9
 MPG.city ~ EngineSize + Weight + Passengers + Price
...
Call:
lm(formula = MPG.city ~ Weight, data = Cars93)

Coefficients:
(Intercept)       Weight
   47.04835     -0.00803