# 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