Executive Salaries

load("EXEXSAL2.Rdata")

names(EXEXSAL2)
##  [1] "ID"  "Y"   "X1"  "X2"  "X3"  "X4"  "X5"  "X6"  "X7"  "X8"  "X9"  "X10"
EXEXSAL2 <-EXEXSAL2[,-1]

names(EXEXSAL2)
##  [1] "Y"   "X1"  "X2"  "X3"  "X4"  "X5"  "X6"  "X7"  "X8"  "X9"  "X10"

 

Backward Elimination

reg_full<-lm(Y~., data=EXEXSAL2)

n <-length(reg_full$residuals)

summary(reg_full)
## 
## Call:
## lm(formula = Y ~ ., data = EXEXSAL2)
## 
## Residuals:
##       Min        1Q    Median        3Q       Max 
## -0.201770 -0.050464  0.004435  0.046826  0.185952 
## 
## Coefficients:
##               Estimate Std. Error t value Pr(>|t|)    
## (Intercept)  1.002e+01  1.481e-01  67.692  < 2e-16 ***
## X1           2.792e-02  1.773e-03  15.745  < 2e-16 ***
## X2           2.903e-02  3.426e-03   8.475 4.57e-13 ***
## X3           2.243e-01  1.708e-02  13.135  < 2e-16 ***
## X4           5.140e-04  4.922e-05  10.443  < 2e-16 ***
## X5           2.048e-03  5.250e-04   3.901 0.000186 ***
## X6          -1.538e-02  1.686e-02  -0.912 0.364124    
## X7          -5.097e-04  1.438e-03  -0.355 0.723795    
## X8          -2.633e-03  5.128e-03  -0.513 0.608896    
## X9          -2.656e-02  2.037e-02  -1.304 0.195613    
## X10         -9.774e-04  2.959e-03  -0.330 0.741955    
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 0.07608 on 89 degrees of freedom
## Multiple R-squared:  0.9229, Adjusted R-squared:  0.9142 
## F-statistic: 106.5 on 10 and 89 DF,  p-value: < 2.2e-16
reg_back_aic <-step(reg_full, direction="backward")
## Start:  AIC=-504.84
## Y ~ X1 + X2 + X3 + X4 + X5 + X6 + X7 + X8 + X9 + X10
## 
##        Df Sum of Sq     RSS     AIC
## - X10   1   0.00063 0.51583 -506.71
## - X7    1   0.00073 0.51593 -506.70
## - X8    1   0.00153 0.51673 -506.54
## - X6    1   0.00482 0.52002 -505.91
## - X9    1   0.00984 0.52504 -504.94
## <none>              0.51520 -504.84
## - X5    1   0.08810 0.60330 -491.05
## - X2    1   0.41581 0.93102 -447.66
## - X4    1   0.63133 1.14653 -426.84
## - X3    1   0.99872 1.51393 -399.05
## - X1    1   1.43512 1.95032 -373.72
## 
## Step:  AIC=-506.71
## Y ~ X1 + X2 + X3 + X4 + X5 + X6 + X7 + X8 + X9
## 
##        Df Sum of Sq     RSS     AIC
## - X7    1   0.00050 0.51633 -508.62
## - X8    1   0.00149 0.51732 -508.43
## - X6    1   0.00448 0.52031 -507.85
## - X9    1   0.00992 0.52575 -506.81
## <none>              0.51583 -506.71
## - X5    1   0.08769 0.60352 -493.01
## - X2    1   0.41593 0.93176 -449.59
## - X4    1   0.63878 1.15461 -428.14
## - X3    1   1.03375 1.54959 -398.72
## - X1    1   1.52826 2.04409 -371.02
## 
## Step:  AIC=-508.62
## Y ~ X1 + X2 + X3 + X4 + X5 + X6 + X8 + X9
## 
##        Df Sum of Sq    RSS     AIC
## - X8    1    0.0015 0.5178 -510.33
## - X6    1    0.0040 0.5203 -509.85
## - X9    1    0.0096 0.5260 -508.77
## <none>              0.5163 -508.62
## - X5    1    0.0898 0.6061 -494.58
## - X2    1    0.4243 0.9406 -450.64
## - X4    1    0.6384 1.1547 -430.13
## - X3    1    1.0503 1.5666 -399.62
## - X1    1    3.9764 4.4927 -294.27
## 
## Step:  AIC=-510.33
## Y ~ X1 + X2 + X3 + X4 + X5 + X6 + X9
## 
##        Df Sum of Sq    RSS     AIC
## - X6    1    0.0033 0.5211 -511.69
## - X9    1    0.0089 0.5267 -510.64
## <none>              0.5178 -510.33
## - X5    1    0.0885 0.6064 -496.55
## - X2    1    0.4230 0.9408 -452.62
## - X4    1    0.6420 1.1598 -431.69
## - X3    1    1.0490 1.5668 -401.61
## - X1    1    3.9749 4.4927 -296.27
## 
## Step:  AIC=-511.69
## Y ~ X1 + X2 + X3 + X4 + X5 + X9
## 
##        Df Sum of Sq    RSS     AIC
## - X9    1    0.0093 0.5304 -511.93
## <none>              0.5211 -511.69
## - X5    1    0.0947 0.6159 -496.99
## - X2    1    0.4347 0.9558 -453.04
## - X4    1    0.6868 1.2079 -429.63
## - X3    1    1.0466 1.5677 -403.55
## - X1    1    3.9718 4.4929 -298.27
## 
## Step:  AIC=-511.93
## Y ~ X1 + X2 + X3 + X4 + X5
## 
##        Df Sum of Sq    RSS     AIC
## <none>              0.5304 -511.93
## - X5    1    0.0879 0.6183 -498.59
## - X2    1    0.4289 0.9594 -454.67
## - X4    1    0.6908 1.2212 -430.53
## - X3    1    1.0656 1.5961 -403.76
## - X1    1    3.9627 4.4932 -300.26
reg_back_bic <-step(reg_full, direction="backward", k=log(n))
## Start:  AIC=-476.18
## Y ~ X1 + X2 + X3 + X4 + X5 + X6 + X7 + X8 + X9 + X10
## 
##        Df Sum of Sq     RSS     AIC
## - X10   1   0.00063 0.51583 -480.66
## - X7    1   0.00073 0.51593 -480.64
## - X8    1   0.00153 0.51673 -480.49
## - X6    1   0.00482 0.52002 -479.85
## - X9    1   0.00984 0.52504 -478.89
## <none>              0.51520 -476.18
## - X5    1   0.08810 0.60330 -465.00
## - X2    1   0.41581 0.93102 -421.61
## - X4    1   0.63133 1.14653 -400.79
## - X3    1   0.99872 1.51393 -372.99
## - X1    1   1.43512 1.95032 -347.67
## 
## Step:  AIC=-480.66
## Y ~ X1 + X2 + X3 + X4 + X5 + X6 + X7 + X8 + X9
## 
##        Df Sum of Sq     RSS     AIC
## - X7    1   0.00050 0.51633 -485.17
## - X8    1   0.00149 0.51732 -484.98
## - X6    1   0.00448 0.52031 -484.40
## - X9    1   0.00992 0.52575 -483.36
## <none>              0.51583 -480.66
## - X5    1   0.08769 0.60352 -469.57
## - X2    1   0.41593 0.93176 -426.14
## - X4    1   0.63878 1.15461 -404.69
## - X3    1   1.03375 1.54959 -375.27
## - X1    1   1.52826 2.04409 -347.58
## 
## Step:  AIC=-485.17
## Y ~ X1 + X2 + X3 + X4 + X5 + X6 + X8 + X9
## 
##        Df Sum of Sq    RSS     AIC
## - X8    1    0.0015 0.5178 -489.49
## - X6    1    0.0040 0.5203 -489.01
## - X9    1    0.0096 0.5260 -487.93
## <none>              0.5163 -485.17
## - X5    1    0.0898 0.6061 -473.74
## - X2    1    0.4243 0.9406 -429.79
## - X4    1    0.6384 1.1547 -409.29
## - X3    1    1.0503 1.5666 -378.78
## - X1    1    3.9764 4.4927 -273.43
## 
## Step:  AIC=-489.49
## Y ~ X1 + X2 + X3 + X4 + X5 + X6 + X9
## 
##        Df Sum of Sq    RSS     AIC
## - X6    1    0.0033 0.5211 -493.46
## - X9    1    0.0089 0.5267 -492.40
## <none>              0.5178 -489.49
## - X5    1    0.0885 0.6064 -478.31
## - X2    1    0.4230 0.9408 -434.39
## - X4    1    0.6420 1.1598 -413.46
## - X3    1    1.0490 1.5668 -383.38
## - X1    1    3.9749 4.4927 -278.04
## 
## Step:  AIC=-493.46
## Y ~ X1 + X2 + X3 + X4 + X5 + X9
## 
##        Df Sum of Sq    RSS     AIC
## - X9    1    0.0093 0.5304 -496.30
## <none>              0.5211 -493.46
## - X5    1    0.0947 0.6159 -481.36
## - X2    1    0.4347 0.9558 -437.41
## - X4    1    0.6868 1.2079 -413.99
## - X3    1    1.0466 1.5677 -387.92
## - X1    1    3.9718 4.4929 -282.64
## 
## Step:  AIC=-496.3
## Y ~ X1 + X2 + X3 + X4 + X5
## 
##        Df Sum of Sq    RSS     AIC
## <none>              0.5304 -496.30
## - X5    1    0.0879 0.6183 -485.57
## - X2    1    0.4289 0.9594 -441.64
## - X4    1    0.6908 1.2212 -417.51
## - X3    1    1.0656 1.5961 -390.74
## - X1    1    3.9627 4.4932 -287.24

 

Forward Selection

reg_forward_start <-lm(Y~1, data=EXEXSAL2)

reg_forward_aic <- step(reg_forward_start,scope=Y~X1+X2+X3+X4+X5+X6+X7+X8+X9+X10, direction="forward" )
## Start:  AIC=-268.57
## Y ~ 1
## 
##        Df Sum of Sq    RSS     AIC
## + X1    1    4.1364 2.5462 -363.06
## + X7    1    2.6488 4.0338 -317.05
## + X3    1    1.0492 5.6335 -283.64
## + X2    1    0.3264 6.3563 -271.57
## + X4    1    0.2897 6.3930 -271.00
## + X5    1    0.2774 6.4052 -270.81
## <none>              6.6827 -268.57
## + X10   1    0.0201 6.6625 -266.87
## + X8    1    0.0181 6.6646 -266.84
## + X6    1    0.0169 6.6657 -266.82
## + X9    1    0.0002 6.6824 -266.57
## 
## Step:  AIC=-363.06
## Y ~ X1
## 
##        Df Sum of Sq    RSS     AIC
## + X3    1   0.87027 1.6760 -402.88
## + X2    1   0.32522 2.2210 -374.72
## + X4    1   0.31253 2.2337 -374.15
## + X5    1   0.26811 2.2781 -372.18
## <none>              2.5462 -363.06
## + X6    1   0.04591 2.5003 -362.87
## + X10   1   0.04132 2.5049 -362.69
## + X8    1   0.01466 2.5316 -361.63
## + X7    1   0.00843 2.5378 -361.39
## + X9    1   0.00381 2.5424 -361.21
## 
## Step:  AIC=-402.88
## Y ~ X1 + X3
## 
##        Df Sum of Sq    RSS     AIC
## + X4    1   0.60068 1.0753 -445.26
## + X2    1   0.28150 1.3945 -419.27
## + X5    1   0.19195 1.4840 -413.04
## + X6    1   0.10205 1.5739 -407.16
## <none>              1.6760 -402.88
## + X8    1   0.00735 1.6686 -401.32
## + X10   1   0.00137 1.6746 -400.96
## + X9    1   0.00022 1.6757 -400.89
## + X7    1   0.00000 1.6760 -400.88
## 
## Step:  AIC=-445.26
## Y ~ X1 + X3 + X4
## 
##        Df Sum of Sq     RSS     AIC
## + X2    1   0.45697 0.61832 -498.59
## + X5    1   0.11593 0.95936 -454.67
## + X6    1   0.02841 1.04688 -445.94
## <none>              1.07529 -445.26
## + X7    1   0.00623 1.06906 -443.84
## + X8    1   0.00622 1.06907 -443.84
## + X10   1   0.00044 1.07485 -443.30
## + X9    1   0.00003 1.07526 -443.26
## 
## Step:  AIC=-498.59
## Y ~ X1 + X3 + X4 + X2
## 
##        Df Sum of Sq     RSS     AIC
## + X5    1  0.087902 0.53041 -511.93
## <none>              0.61832 -498.59
## + X6    1  0.009688 0.60863 -498.17
## + X9    1  0.002451 0.61587 -496.99
## + X8    1  0.001376 0.61694 -496.82
## + X7    1  0.000343 0.61797 -496.65
## + X10   1  0.000000 0.61832 -496.59
## 
## Step:  AIC=-511.93
## Y ~ X1 + X3 + X4 + X2 + X5
## 
##        Df Sum of Sq     RSS     AIC
## <none>              0.53041 -511.93
## + X9    1 0.0092875 0.52113 -511.69
## + X6    1 0.0037568 0.52666 -510.64
## + X10   1 0.0003588 0.53006 -509.99
## + X8    1 0.0002463 0.53017 -509.97
## + X7    1 0.0000122 0.53040 -509.93
reg_forward_bic <- step(reg_forward_start,scope=Y~X1+X2+X3+X4+X5+X6+X7+X8+X9+X10, direction="forward", k=log(n) )
## Start:  AIC=-265.96
## Y ~ 1
## 
##        Df Sum of Sq    RSS     AIC
## + X1    1    4.1364 2.5462 -357.85
## + X7    1    2.6488 4.0338 -311.84
## + X3    1    1.0492 5.6335 -278.43
## + X2    1    0.3264 6.3563 -266.36
## <none>              6.6827 -265.96
## + X4    1    0.2897 6.3930 -265.79
## + X5    1    0.2774 6.4052 -265.60
## + X10   1    0.0201 6.6625 -261.66
## + X8    1    0.0181 6.6646 -261.63
## + X6    1    0.0169 6.6657 -261.61
## + X9    1    0.0002 6.6824 -261.36
## 
## Step:  AIC=-357.85
## Y ~ X1
## 
##        Df Sum of Sq    RSS     AIC
## + X3    1   0.87027 1.6760 -395.06
## + X2    1   0.32522 2.2210 -366.91
## + X4    1   0.31253 2.2337 -366.34
## + X5    1   0.26811 2.2781 -364.37
## <none>              2.5462 -357.85
## + X6    1   0.04591 2.5003 -355.06
## + X10   1   0.04132 2.5049 -354.88
## + X8    1   0.01466 2.5316 -353.82
## + X7    1   0.00843 2.5378 -353.57
## + X9    1   0.00381 2.5424 -353.39
## 
## Step:  AIC=-395.06
## Y ~ X1 + X3
## 
##        Df Sum of Sq    RSS     AIC
## + X4    1   0.60068 1.0753 -434.84
## + X2    1   0.28150 1.3945 -408.85
## + X5    1   0.19195 1.4840 -402.62
## + X6    1   0.10205 1.5739 -396.74
## <none>              1.6760 -395.06
## + X8    1   0.00735 1.6686 -390.90
## + X10   1   0.00137 1.6746 -390.54
## + X9    1   0.00022 1.6757 -390.47
## + X7    1   0.00000 1.6760 -390.46
## 
## Step:  AIC=-434.84
## Y ~ X1 + X3 + X4
## 
##        Df Sum of Sq     RSS     AIC
## + X2    1   0.45697 0.61832 -485.57
## + X5    1   0.11593 0.95936 -441.64
## <none>              1.07529 -434.84
## + X6    1   0.02841 1.04688 -432.91
## + X7    1   0.00623 1.06906 -430.81
## + X8    1   0.00622 1.06907 -430.81
## + X10   1   0.00044 1.07485 -430.27
## + X9    1   0.00003 1.07526 -430.23
## 
## Step:  AIC=-485.57
## Y ~ X1 + X3 + X4 + X2
## 
##        Df Sum of Sq     RSS     AIC
## + X5    1  0.087902 0.53041 -496.30
## <none>              0.61832 -485.57
## + X6    1  0.009688 0.60863 -482.54
## + X9    1  0.002451 0.61587 -481.36
## + X8    1  0.001376 0.61694 -481.18
## + X7    1  0.000343 0.61797 -481.02
## + X10   1  0.000000 0.61832 -480.96
## 
## Step:  AIC=-496.3
## Y ~ X1 + X3 + X4 + X2 + X5
## 
##        Df Sum of Sq     RSS     AIC
## <none>              0.53041 -496.30
## + X9    1 0.0092875 0.52113 -493.46
## + X6    1 0.0037568 0.52666 -492.40
## + X10   1 0.0003588 0.53006 -491.76
## + X8    1 0.0002463 0.53017 -491.74
## + X7    1 0.0000122 0.53040 -491.69

Stepwise regression

reg_forward_step <- step(reg_forward_start,scope=Y~X1+X2+X3+X4+X5+X6+X7+X8+X9+X10, direction="both" )
## Start:  AIC=-268.57
## Y ~ 1
## 
##        Df Sum of Sq    RSS     AIC
## + X1    1    4.1364 2.5462 -363.06
## + X7    1    2.6488 4.0338 -317.05
## + X3    1    1.0492 5.6335 -283.64
## + X2    1    0.3264 6.3563 -271.57
## + X4    1    0.2897 6.3930 -271.00
## + X5    1    0.2774 6.4052 -270.81
## <none>              6.6827 -268.57
## + X10   1    0.0201 6.6625 -266.87
## + X8    1    0.0181 6.6646 -266.84
## + X6    1    0.0169 6.6657 -266.82
## + X9    1    0.0002 6.6824 -266.57
## 
## Step:  AIC=-363.06
## Y ~ X1
## 
##        Df Sum of Sq    RSS     AIC
## + X3    1    0.8703 1.6760 -402.88
## + X2    1    0.3252 2.2210 -374.72
## + X4    1    0.3125 2.2337 -374.15
## + X5    1    0.2681 2.2781 -372.18
## <none>              2.5462 -363.06
## + X6    1    0.0459 2.5003 -362.87
## + X10   1    0.0413 2.5049 -362.69
## + X8    1    0.0147 2.5316 -361.63
## + X7    1    0.0084 2.5378 -361.39
## + X9    1    0.0038 2.5424 -361.21
## - X1    1    4.1364 6.6827 -268.57
## 
## Step:  AIC=-402.88
## Y ~ X1 + X3
## 
##        Df Sum of Sq    RSS     AIC
## + X4    1    0.6007 1.0753 -445.26
## + X2    1    0.2815 1.3945 -419.27
## + X5    1    0.1919 1.4840 -413.04
## + X6    1    0.1021 1.5739 -407.16
## <none>              1.6760 -402.88
## + X8    1    0.0073 1.6686 -401.32
## + X10   1    0.0014 1.6746 -400.96
## + X9    1    0.0002 1.6757 -400.89
## + X7    1    0.0000 1.6760 -400.88
## - X3    1    0.8703 2.5462 -363.06
## - X1    1    3.9575 5.6335 -283.64
## 
## Step:  AIC=-445.26
## Y ~ X1 + X3 + X4
## 
##        Df Sum of Sq    RSS     AIC
## + X2    1    0.4570 0.6183 -498.59
## + X5    1    0.1159 0.9594 -454.67
## + X6    1    0.0284 1.0469 -445.94
## <none>              1.0753 -445.26
## + X7    1    0.0062 1.0691 -443.84
## + X8    1    0.0062 1.0691 -443.84
## + X10   1    0.0004 1.0748 -443.30
## + X9    1    0.0000 1.0753 -443.26
## - X4    1    0.6007 1.6760 -402.88
## - X3    1    1.1584 2.2337 -374.15
## - X1    1    3.9592 5.0345 -292.89
## 
## Step:  AIC=-498.59
## Y ~ X1 + X3 + X4 + X2
## 
##        Df Sum of Sq    RSS     AIC
## + X5    1    0.0879 0.5304 -511.93
## <none>              0.6183 -498.59
## + X6    1    0.0097 0.6086 -498.17
## + X9    1    0.0025 0.6159 -496.99
## + X8    1    0.0014 0.6169 -496.82
## + X7    1    0.0003 0.6180 -496.65
## + X10   1    0.0000 0.6183 -496.59
## - X2    1    0.4570 1.0753 -445.26
## - X4    1    0.7761 1.3945 -419.27
## - X3    1    1.1508 1.7692 -395.47
## - X1    1    3.9635 4.5818 -300.31
## 
## Step:  AIC=-511.93
## Y ~ X1 + X3 + X4 + X2 + X5
## 
##        Df Sum of Sq    RSS     AIC
## <none>              0.5304 -511.93
## + X9    1    0.0093 0.5211 -511.69
## + X6    1    0.0038 0.5267 -510.64
## + X10   1    0.0004 0.5301 -509.99
## + X8    1    0.0002 0.5302 -509.97
## + X7    1    0.0000 0.5304 -509.93
## - X5    1    0.0879 0.6183 -498.59
## - X2    1    0.4289 0.9594 -454.67
## - X4    1    0.6908 1.2212 -430.53
## - X3    1    1.0656 1.5961 -403.76
## - X1    1    3.9627 4.4932 -300.26
summary(reg_forward_step)$adj.r.squared
## [1] 0.9164065
summary(reg_forward_step)$r.squared
## [1] 0.9206284