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 -0.0043  0.0219  0.0042 -0.0038 -0.0028
## X2 -0.0043  1.0000 -0.0020  0.0000 -0.0016 -0.0010
## X3  0.0219 -0.0020  1.0000  0.0021 -0.0022 -0.0047
## X4  0.0042  0.0000  0.0021  1.0000 -0.0038  0.0011
## X5 -0.0038 -0.0016 -0.0022 -0.0038  1.0000 -0.0019
## X6 -0.0028 -0.0010 -0.0047  0.0011 -0.0019  1.0000
names(Xsum) <- M1:M2
Xsum %>%
  summary %>%
  round(2) 
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##    2.04   16.44   20.40   21.04   24.96   67.49
Xsum %>%
  sd %>%
  round(2)
## [1] 6.42
Xsum %>%
  `<=`(5) %>%
  which %>%
  `[`(Xsum, .) %>%
  round(2)
## 3001529 3006931 3023635 3029548 3032626 3053411 3058281 3058469 3068636 3068890 
##    3.12    4.43    4.49    3.78    5.00    4.95    4.71    3.45    4.88    4.48 
## 3074553 3094409 3107543 3116780 3119729 3144402 3155913 3156100 3166288 3175246 
##    3.89    4.52    4.21    4.50    4.88    3.36    4.40    4.93    4.65    4.99 
## 3186466 3189686 3191188 3198954 3201735 3212532 3224636 3224952 3233885 3260876 
##    4.01    4.99    4.60    4.96    4.50    4.49    4.40    4.99    4.41    4.96 
## 3269587 3272527 3274098 3287540 3307304 3309679 3313741 3320842 3347610 3364242 
##    4.97    4.92    2.85    4.20    4.99    4.33    4.96    4.04    4.48    4.76 
## 3371025 3377687 3387275 3387739 3388200 3404747 3411318 3413447 3414552 3432983 
##    4.52    4.87    4.70    3.98    4.60    4.94    4.16    4.92    3.42    3.80 
## 3472872 3491107 3497339 3510038 3517220 3518843 3527648 3528203 3548758 3557172 
##    3.63    4.45    4.48    4.49    4.89    5.00    4.23    4.90    4.42    4.71 
## 3559076 3577912 3597970 3609069 3609183 3609292 3629335 3631310 3633979 3643534 
##    4.30    2.96    4.70    4.82    4.68    5.00    4.29    3.22    4.54    4.91 
## 3646753 3654218 3656673 3659497 3669487 3687616 3687798 3691266 3697259 3715954 
##    4.97    4.34    3.81    4.50    3.38    4.66    4.62    4.71    3.66    4.82 
## 3724684 3730660 3750954 3752240 3765463 3766329 3767471 3781170 3792218 3802909 
##    2.04    2.96    4.35    4.16    4.18    4.47    4.67    3.58    4.85    4.72 
## 3810664 3821430 3828152 3834899 3840675 3844096 3857828 3858320 3871710 3875722 
##    4.34    4.86    4.93    4.48    4.99    4.82    4.75    4.57    5.00    3.92 
## 3882185 3886216 3896101 3900040 3906774 3926931 3944272 3955824 3968062 3979209 
##    4.32    4.60    4.49    4.97    3.81    4.30    4.08    4.40    4.47    4.98 
## 3980055 3987806 
##    4.91    4.80
Xmin <- names(Xsum[which(Xsum == min(Xsum))])
Xmin
## [1] "3724684"

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] 0.8712759 0.2058171 0.0000000 0.1418978 0.7164201 0.1020702
## 
## $Xsum
## [1] 2.037481

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 16 34 31 36 18 64 44
Black 16 34 33 38 17 68 37
X1min <- tbl1 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X1min
## X-squared 
## 0.8712759

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 122 121
Black 117 126
X2min <- tbl2 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X2min
## X-squared 
## 0.2058171

학적 상태

tbl3 <- class_roll$status %>%
  table(class_roll$group, .) 
tbl3 %>%
  pander
  학생 휴학
Red 239 4
Black 239 4
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 207 36
Black 204 39
X4min <- tbl4 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X4min
## X-squared 
## 0.1418978

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 20 23 21 26 31 21 21 29 25 26
Black 21 20 24 27 28 23 21 29 24 26
X5min <- tbl5 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X5min
## X-squared 
## 0.7164201

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 45 42 15 141
Black 47 41 16 139
X6min <- tbl6 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X6min
## X-squared 
## 0.1020702

Sum of Chi_Squares

Xsum_min <- X1min + X2min + X3min + X4min + X5min + X6min
Xsum_min
## X-squared 
##  2.037481