Data

Search for Best Configuration

M1 <- 3000001
M2 <- 4000000
Xsum <- numeric(0)
Values_mat <- numeric(0)
for(k in M1:M2){
  set.seed(k)
  N <- nrow(class_roll) 
  class_roll$group <- 
    sample(1:N) %%
    2 %>%
    factor(levels = c(0, 1), labels = c("Red", "Black"))
  Xsum <- c(Xsum, red_and_black(class_roll)$Xsum)
  Values_mat <- rbind(Values_mat, red_and_black(class_roll)$Values)
}
colnames(Values_mat) <- paste0("X", 1:6)
# Values_mat
# pairs(Values_mat)
cor(Values_mat) %>%
  round(4)
##         X1      X2      X3      X4      X5      X6
## X1  1.0000  0.0019  0.0387 -0.0003  0.0047 -0.0035
## X2  0.0019  1.0000 -0.0012  0.0004  0.0001 -0.0013
## X3  0.0387 -0.0012  1.0000  0.0001  0.0065 -0.0005
## X4 -0.0003  0.0004  0.0001  1.0000  0.0007 -0.0017
## X5  0.0047  0.0001  0.0065  0.0007  1.0000 -0.0002
## X6 -0.0035 -0.0013 -0.0005 -0.0017 -0.0002  1.0000
names(Xsum) <- M1:M2
Xsum %>%
  summary %>%
  round(2) 
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##    2.68   16.37   20.38   21.04   24.98   68.83
Xsum %>%
  sd %>%
  round(2)
## [1] 6.49
Xsum %>%
  `<=`(5) %>%
  which %>%
  `[`(Xsum, .) %>%
  round(2)
## 3011945 3030895 3039337 3040677 3044581 3045770 3051949 3051986 3060492 3063843 
##    4.82    4.93    4.11    4.18    4.45    3.28    4.92    4.27    2.68    3.27 
## 3065739 3070389 3072720 3074713 3076562 3096410 3101859 3107242 3116285 3143850 
##    4.65    4.26    4.93    4.73    3.91    4.84    4.94    4.63    4.29    4.88 
## 3150515 3152354 3156043 3160597 3163335 3163847 3177010 3177921 3178744 3180123 
##    4.61    4.85    4.77    4.13    4.78    4.55    3.91    4.87    4.52    4.20 
## 3189991 3190029 3201026 3202681 3221696 3238242 3241767 3247887 3252356 3257166 
##    4.04    4.91    3.79    4.42    4.99    4.76    3.46    3.70    4.93    4.49 
## 3280105 3290978 3291019 3298764 3309464 3312312 3313069 3316078 3318179 3318278 
##    4.31    3.30    4.80    4.92    4.89    4.59    4.33    4.92    4.88    4.56 
## 3327376 3332417 3333690 3336511 3345489 3346823 3348100 3349351 3350109 3363828 
##    4.76    4.10    4.68    4.65    4.46    4.77    4.95    4.20    4.98    4.98 
## 3366213 3371733 3374012 3377187 3386277 3393644 3399958 3404522 3431784 3454906 
##    2.82    4.65    4.49    4.88    4.46    4.40    4.47    4.98    3.54    3.79 
## 3458658 3459389 3465054 3471415 3474796 3475907 3477293 3478384 3479520 3484488 
##    3.62    4.82    3.82    4.74    4.99    4.52    3.83    4.80    4.79    2.94 
## 3487735 3490250 3495135 3497840 3500345 3502344 3503172 3508084 3510898 3531962 
##    4.76    4.59    4.85    4.39    4.95    4.77    4.60    4.78    4.82    4.96 
## 3539210 3543080 3551141 3566929 3586848 3591154 3602706 3606106 3606490 3609735 
##    3.36    4.20    4.50    4.75    4.48    3.94    4.41    4.18    4.87    4.23 
## 3614914 3622783 3639852 3649366 3658805 3659079 3680942 3685760 3687726 3693944 
##    4.54    3.60    4.74    4.32    4.97    2.96    4.51    3.99    4.10    4.47 
## 3697590 3702463 3719552 3729782 3738667 3739164 3751741 3758205 3762712 3763100 
##    4.35    4.89    4.54    4.50    4.97    4.00    4.97    4.53    4.87    4.72 
## 3781304 3783655 3784356 3795987 3799284 3802008 3803378 3810370 3813612 3815134 
##    4.91    3.07    3.35    4.84    4.83    4.35    3.36    4.85    4.90    3.72 
## 3834890 3835684 3844642 3860317 3874658 3882736 3883208 3888548 3895360 3896939 
##    3.19    4.17    4.25    4.12    4.32    4.90    4.55    4.74    4.35    4.90 
## 3905118 3910233 3915893 3936759 3940864 3943956 3945835 3956867 3957451 3981733 
##    4.24    4.86    4.26    4.84    4.09    4.60    4.80    4.62    4.15    4.80 
## 3987305 3995198 3997030 3997482 
##    4.89    4.99    4.41    3.66
Xmin <- names(Xsum[which(Xsum == min(Xsum))])
Xmin
## [1] "3060492"

Plot

hist(Xsum, prob = TRUE, nclass = 30, xlim = c(0, 50), ylim = c(0, 0.065))
x <- seq(0, 50, by = 0.1)
lines(x, dchisq(x, df = 21), col = "red")
legend("topright", inset = 0.05, legend = c("Xsum", "Chi-square(21)"), col = c("black", "red"), lty = 1)

plot(density(Xsum), xlim = c(0, 50), main = "Density Estimation of Xsum")
lines(x, dchisq(x, df = 21), col = "red")
legend("topright", inset = 0.05, legend = c("Xsum", "Chi-square(21)"), col = c("black", "red"), lty = 1)

Randomization

set.seed(Xmin)
N <- nrow(class_roll) 
class_roll$group <- 
  sample(1:N) %%
  2 %>%
  factor(levels = c(0, 1), labels = c("Red", "Black"))
red_and_black(class_roll)
## $Values
## [1] 0.98112648 0.16247639 0.00000000 0.04853833 1.15611756 0.33010095
## 
## $Xsum
## [1] 2.67836

학번

class_roll$id_2 <-
  class_roll$id %>%
  ifelse(. <= 2015, "2015", .)
tbl1 <- class_roll %$%
  table(.$group, .$id_2 %>% substr(1, 4)) %>%
  `colnames<-`(c("2015 이전", 2016:2021)) 
tbl1 %>%
  pander
  2015 이전 2016 2017 2018 2019 2020 2021
Red 18 28 25 55 18 49 115
Black 19 30 30 53 20 49 107
X1min <- tbl1 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X1min
## X-squared 
## 0.9811265

학번 홀짝

tbl2 <- class_roll$id %>%
  as.numeric %>%
  `%%`(2) %>%
  factor(levels = c(1, 0), labels = c("홀", "짝")) %>%
  table(class_roll$group, .) 
tbl2 %>%
  pander
 
Red 152 156
Black 147 161
X2min <- tbl2 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X2min
## X-squared 
## 0.1624764

학적 상태

tbl3 <- class_roll$status %>%
  table(class_roll$group, .) 
tbl3 %>%
  pander
  학생 휴학
Red 278 30
Black 278 30
X3min <- tbl3 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X3min
## X-squared 
##         0

e-mail 서비스업체

tbl4 <- class_roll$email %>%
  strsplit("@", fixed = TRUE) %>%
  sapply("[", 2) %>%
  `==`("naver.com") %>%
  ifelse("네이버", "기타서비스") %>%
  factor(levels = c("네이버", "기타서비스")) %>%
  table(class_roll$group, .) 
tbl4 %>%
  pander
  네이버 기타서비스
Red 258 50
Black 260 48
X4min <- tbl4 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X4min
##  X-squared 
## 0.04853833

전화번호의 분포

cut_label <- paste(paste0(0:9, "000"), paste0(0:9, "999"), 
                   sep = "~")
tbl5 <- class_roll$cell_no %>%
  substr(start = 8, stop = 11) %>%
  sapply(as.numeric) %>%
  cut(labels = cut_label, 
      breaks = seq(0, 10000, by = 1000)) %>%
  table(class_roll$group, .) 
tbl5 %>%
  pander
  0000~0999 1000~1999 2000~2999 3000~3999 4000~4999 5000~5999 6000~6999 7000~7999 8000~8999 9000~9999
Red 24 29 34 26 26 33 28 34 40 34
Black 23 33 34 27 25 31 27 40 36 32
X5min <- tbl5 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X5min
## X-squared 
##  1.156118

성씨 분포

f_name <- class_roll$name %>%
  substring(first = 1, last = 1) 
tbl6 <- f_name %>%
  `%in%`(c("김", "이", "박")) %>%
  ifelse(f_name, "기타") %>%
  factor(levels = c("김", "이", "박", "기타")) %>%
  table(class_roll$group, .) 
tbl6 %>%
  pander
  기타
Red 65 48 26 169
Black 63 47 23 175
X6min <- tbl6 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X6min
## X-squared 
## 0.3301009

Sum of Chi_Squares

Xsum_min <- X1min + X2min + X3min + X4min + X5min + X6min
Xsum_min
## X-squared 
##   2.67836