Summary Statistics
|
|
|
Statistic
|
N
|
Mean
|
St. Dev.
|
Min
|
Max
|
|
|
|
wage
|
663
|
988.48
|
406.51
|
115
|
3,078
|
|
hours
|
663
|
44.06
|
7.16
|
25
|
80
|
|
IQ
|
663
|
102.48
|
14.69
|
54
|
145
|
|
KWW
|
663
|
36.19
|
7.53
|
13
|
56
|
|
educ
|
663
|
13.68
|
2.23
|
9
|
18
|
|
exper
|
663
|
11.40
|
4.26
|
1
|
22
|
|
tenure
|
663
|
7.22
|
5.06
|
0
|
22
|
|
age
|
663
|
32.98
|
3.06
|
28
|
38
|
|
married
|
663
|
0.90
|
0.30
|
0
|
1
|
|
black
|
663
|
0.08
|
0.27
|
0
|
1
|
|
south
|
663
|
0.32
|
0.47
|
0
|
1
|
|
urban
|
663
|
0.72
|
0.45
|
0
|
1
|
|
sibs
|
663
|
2.85
|
2.24
|
0
|
14
|
|
brthord
|
663
|
2.18
|
1.49
|
1
|
10
|
|
meduc
|
663
|
10.83
|
2.82
|
0
|
18
|
|
feduc
|
663
|
10.27
|
3.29
|
0
|
18
|
|
lwage
|
663
|
6.81
|
0.41
|
4.74
|
8.03
|
|
|
hist(
lalonde$re78,
main = "Histogram of re78",
xlab = "re78",
ylab = "Count",
breaks = 30
)
OLS1 <- lm_robust(re78 ~ treat, data = lalonde)
OLS2 <- lm_robust(
re78 ~ treat + age + educ + hisp + married + nodegr,
data = lalonde
)
summary(OLS1)
##
## Call:
## lm_robust(formula = re78 ~ treat, data = lalonde)
##
## Standard error type: HC2
##
## Coefficients:
## Estimate Std. Error t value Pr(>|t|) CI Lower CI Upper DF
## (Intercept) 4555 340.1 13.393 1.391e-34 3886.4 5223 443
## treat 1794 671.0 2.674 7.769e-03 475.6 3113 443
##
## Multiple R-squared: 0.01782 , Adjusted R-squared: 0.01561
## F-statistic: 7.151 on 1 and 443 DF, p-value: 0.007769
summary(OLS2)
##
## Call:
## lm_robust(formula = re78 ~ treat + age + educ + hisp + married +
## nodegr, data = lalonde)
##
## Standard error type: HC2
##
## Coefficients:
## Estimate Std. Error t value Pr(>|t|) CI Lower CI Upper DF
## (Intercept) -531.64 3121.97 -0.1703 0.86486 -6667.535 5604.3 438
## treat 1711.89 673.74 2.5409 0.01140 387.714 3036.1 438
## age 49.11 41.61 1.1804 0.23848 -32.662 130.9 438
## educ 387.24 197.24 1.9633 0.05024 -0.406 774.9 438
## hisp 2133.42 1018.33 2.0950 0.03674 132.006 4134.8 438
## married 97.00 887.89 0.1093 0.91305 -1648.054 1842.1 438
## nodegr -353.94 1044.07 -0.3390 0.73477 -2405.955 1698.1 438
##
## Multiple R-squared: 0.04002 , Adjusted R-squared: 0.02687
## F-statistic: 2.548 on 6 and 438 DF, p-value: 0.01954