Data

Search for Best Configuration

M1 <- 9000001
M2 <- 10000000
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 -0.0031  0.0216  0.0055 -0.0032 -0.0040
## X2 -0.0031  1.0000 -0.0016 -0.0020 -0.0018 -0.0014
## X3  0.0216 -0.0016  1.0000  0.0032 -0.0023 -0.0038
## X4  0.0055 -0.0020  0.0032  1.0000 -0.0038  0.0024
## X5 -0.0032 -0.0018 -0.0023 -0.0038  1.0000 -0.0033
## X6 -0.0040 -0.0014 -0.0038  0.0024 -0.0033  1.0000
names(Xsum) <- M1:M2
Xsum %>%
  summary %>%
  round(2) 
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##    3.33   16.45   20.41   21.05   24.97   66.24
Xsum %>%
  sd %>%
  round(2)
## [1] 6.42
Xsum %>%
  `<=`(5) %>%
  which %>%
  `[`(Xsum, .) %>%
  round(2)
## 9014747 9025498 9026846 9027585 9030344 9039552 9042099 9047817 9049182 9050962 
##    4.52    4.90    4.12    4.93    4.59    4.99    4.72    4.44    4.41    4.87 
## 9063774 9066492 9067290 9067416 9086979 9104711 9105510 9111870 9115100 9115874 
##    4.93    4.69    4.92    4.57    4.58    4.11    3.74    4.69    4.61    4.23 
## 9128242 9135034 9135341 9140445 9141799 9152627 9174459 9196695 9200887 9209791 
##    4.44    4.98    4.55    4.56    4.38    3.33    4.99    3.58    4.65    4.88 
## 9218795 9231575 9246452 9247414 9263165 9264226 9265007 9269737 9276181 9288037 
##    4.08    4.29    4.78    4.61    4.28    4.72    4.79    4.18    4.88    4.89 
## 9296134 9298497 9304464 9317634 9319980 9333840 9343067 9349852 9351219 9355608 
##    4.72    4.97    4.78    4.96    4.89    4.93    4.66    4.28    3.64    4.71 
## 9387442 9428800 9438268 9452690 9463212 9479540 9490675 9492427 9498169 9502562 
##    4.64    3.84    4.32    4.98    4.10    4.90    4.12    4.65    4.92    4.91 
## 9508861 9511900 9522935 9531496 9533062 9534750 9545731 9550374 9563497 9565888 
##    4.00    4.88    4.65    3.76    4.43    4.60    3.74    4.40    4.77    4.60 
## 9570240 9570777 9588013 9588079 9591059 9593923 9596398 9599690 9604409 9607065 
##    4.93    4.05    3.73    4.66    4.93    4.07    4.09    4.83    4.93    4.88 
## 9611116 9614562 9629204 9635510 9641187 9658848 9666385 9671010 9673681 9682778 
##    4.96    4.95    4.84    4.87    4.60    4.73    4.84    4.95    4.79    4.76 
## 9689874 9699870 9700299 9718002 9719772 9730313 9731076 9732787 9738273 9771604 
##    4.48    4.88    4.69    4.77    4.70    3.94    4.91    4.57    4.23    4.90 
## 9774032 9780628 9785692 9788621 9818004 9831831 9832587 9838787 9846848 9851887 
##    4.71    4.22    4.85    4.04    3.78    4.66    4.81    4.99    4.86    4.81 
## 9854791 9867180 9869644 9875693 9887384 9889104 9911394 9914761 9923095 9931793 
##    4.82    4.73    4.83    4.98    4.62    4.66    4.44    4.65    4.61    4.68 
## 9935182 9966390 9973555 9986368 
##    4.54    4.88    4.91    4.83
Xmin <- names(Xsum[which(Xsum == min(Xsum))])
Xmin
## [1] "9152627"

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] 1.30218171 0.07409415 0.50836820 0.01576642 1.19297371 0.23250502
## 
## $Xsum
## [1] 3.325889

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 15 35 32 37 18 62 44
Black 17 33 32 37 17 70 37
X1min <- tbl1 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X1min
## X-squared 
##  1.302182

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 121 122
Black 118 125
X2min <- tbl2 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X2min
##  X-squared 
## 0.07409415

학적 상태

tbl3 <- class_roll$status %>%
  table(class_roll$group, .) 
tbl3 %>%
  pander
  학생 휴학
Red 238 5
Black 240 3
X3min <- tbl3 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X3min
## X-squared 
## 0.5083682

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 205 38
Black 206 37
X4min <- tbl4 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X4min
##  X-squared 
## 0.01576642

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 23 20 23 26 31 21 21 28 24 26
Black 18 23 22 27 28 23 21 30 25 26
X5min <- tbl5 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X5min
## X-squared 
##  1.192974

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 48 41 15 139
Black 44 42 16 141
X6min <- tbl6 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X6min
## X-squared 
##  0.232505

Sum of Chi_Squares

Xsum_min <- X1min + X2min + X3min + X4min + X5min + X6min
Xsum_min
## X-squared 
##  3.325889