Data

Search for Best Configuration

M1 <- 6000001
M2 <- 7000000
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  0.0028  0.0356 -0.0032  0.0036 -0.0012
## X2  0.0028  1.0000 -0.0010  0.0005  0.0003 -0.0003
## X3  0.0356 -0.0010  1.0000  0.0002  0.0055  0.0009
## X4 -0.0032  0.0005  0.0002  1.0000 -0.0008 -0.0026
## X5  0.0036  0.0003  0.0055 -0.0008  1.0000  0.0022
## X6 -0.0012 -0.0003  0.0009 -0.0026  0.0022  1.0000
names(Xsum) <- M1:M2
Xsum %>%
  summary %>%
  round(2) 
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##    2.34   16.38   20.37   21.04   24.98   62.66
Xsum %>%
  sd %>%
  round(2)
## [1] 6.49
Xsum %>%
  `<=`(5) %>%
  which %>%
  `[`(Xsum, .) %>%
  round(2)
## 6006793 6035732 6042800 6045105 6046704 6048669 6056226 6062504 6074178 6077413 
##    2.34    4.78    4.00    4.99    4.49    4.87    4.67    4.78    4.54    4.96 
## 6083687 6092746 6099327 6104729 6105175 6127518 6136712 6154477 6162447 6163866 
##    4.87    4.78    4.98    4.83    4.54    4.86    4.45    4.18    3.99    4.61 
## 6164354 6180486 6183641 6196543 6204094 6209861 6211412 6212923 6230249 6233107 
##    4.92    4.37    3.98    4.99    4.75    4.58    4.12    4.69    4.87    4.88 
## 6240529 6252563 6257968 6260446 6262994 6273822 6277963 6278442 6279450 6285514 
##    4.71    4.90    4.96    3.60    4.89    4.15    3.18    4.29    4.55    4.08 
## 6292152 6294049 6297767 6302130 6304737 6308341 6332600 6338444 6340437 6352855 
##    4.91    4.64    4.18    4.77    4.56    4.92    3.46    4.56    4.74    4.61 
## 6353197 6368958 6383032 6388080 6389417 6393455 6394483 6400991 6404664 6406241 
##    3.34    4.50    4.90    4.45    4.63    4.45    4.44    4.30    4.78    4.22 
## 6429248 6431556 6439065 6441485 6442577 6447095 6450903 6464071 6470779 6483886 
##    4.54    4.66    4.41    4.37    3.21    4.88    4.83    4.99    4.93    3.84 
## 6489159 6500354 6503264 6519456 6520367 6521936 6530044 6531366 6550569 6551738 
##    4.12    4.91    4.51    4.87    4.61    4.36    4.98    4.97    4.46    4.90 
## 6558534 6559431 6559467 6563347 6573405 6595190 6601656 6611619 6614172 6626548 
##    4.52    4.92    4.08    2.95    4.04    4.06    3.58    4.10    3.86    4.82 
## 6634825 6636123 6637879 6640472 6670865 6687186 6691086 6692690 6705198 6705458 
##    4.27    3.89    4.90    4.99    4.83    4.81    4.91    4.85    4.78    4.07 
## 6707330 6713683 6717340 6732782 6741032 6743134 6746098 6751815 6754113 6772384 
##    4.92    4.18    4.95    4.85    4.58    4.92    4.35    4.62    4.64    4.29 
## 6796909 6799948 6808846 6811235 6816264 6823136 6824480 6855722 6864225 6867702 
##    3.93    4.53    4.41    4.97    4.89    4.89    4.91    4.73    4.80    4.83 
## 6872281 6872928 6899646 6920507 6921686 6923109 6923961 6940779 6951899 6953678 
##    4.60    4.97    4.19    4.15    4.90    4.61    5.00    4.70    4.10    4.83 
## 6963103 6963538 6970489 6972746 6974106 6981370 6981589 6984584 6988382 6994830 
##    4.73    4.51    4.62    4.70    4.73    4.75    4.15    4.73    4.39    4.02 
## 6996259 
##    4.66
Xmin <- names(Xsum[which(Xsum == min(Xsum))])
Xmin
## [1] "6006793"

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] 0.45477490 0.52642351 0.07386091 0.04853833 1.03852916 0.20244611
## 
## $Xsum
## [1] 2.344573

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 19 30 27 54 18 51 109
Black 18 28 28 54 20 47 113
X1min <- tbl1 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X1min
## X-squared 
## 0.4547749

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 145 163
Black 154 154
X2min <- tbl2 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X2min
## X-squared 
## 0.5264235

학적 상태

tbl3 <- class_roll$status %>%
  table(class_roll$group, .) 
tbl3 %>%
  pander
  학생 휴학
Red 279 29
Black 277 31
X3min <- tbl3 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X3min
##  X-squared 
## 0.07386091

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 260 48
Black 258 50
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 32 32 24 26 33 29 37 38 33
Black 23 30 36 29 25 31 26 37 38 33
X5min <- tbl5 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X5min
## X-squared 
##  1.038529

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 66 48 24 170
Black 62 47 25 174
X6min <- tbl6 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X6min
## X-squared 
## 0.2024461

Sum of Chi_Squares

Xsum_min <- X1min + X2min + X3min + X4min + X5min + X6min
Xsum_min
## X-squared 
##  2.344573