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 -0.0026  0.0217  0.0056 -0.0030 -0.0051
## X2 -0.0026  1.0000 -0.0019 -0.0014 -0.0033 -0.0014
## X3  0.0217 -0.0019  1.0000  0.0033 -0.0011 -0.0050
## X4  0.0056 -0.0014  0.0033  1.0000 -0.0043  0.0028
## X5 -0.0030 -0.0033 -0.0011 -0.0043  1.0000 -0.0014
## X6 -0.0051 -0.0014 -0.0050  0.0028 -0.0014  1.0000
names(Xsum) <- M1:M2
Xsum %>%
  summary %>%
  round(2) 
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##    2.93   16.44   20.41   21.05   24.97   66.37
Xsum %>%
  sd %>%
  round(2)
## [1] 6.42
Xsum %>%
  `<=`(5) %>%
  which %>%
  `[`(Xsum, .) %>%
  round(2)
## 6008112 6027299 6029938 6042403 6045613 6049872 6060975 6066424 6098694 6111095 
##    4.96    4.56    4.18    4.32    4.97    4.38    4.78    4.76    4.14    4.74 
## 6111184 6118158 6128676 6130218 6143576 6149493 6151277 6162530 6185861 6191550 
##    4.33    4.37    4.92    4.25    4.33    4.56    4.83    4.68    4.93    3.57 
## 6199486 6200302 6209055 6212713 6215903 6222274 6225154 6229436 6229962 6231204 
##    4.90    4.54    4.60    4.89    4.38    4.88    4.93    4.10    4.85    4.60 
## 6239179 6263533 6274156 6279237 6282216 6282433 6289948 6294445 6294839 6299575 
##    2.93    4.24    4.99    4.74    4.85    4.85    4.49    4.37    4.64    4.89 
## 6306463 6328658 6351364 6356430 6358756 6374481 6376474 6381729 6383113 6384188 
##    4.63    4.12    3.52    4.05    4.95    4.61    4.68    4.77    4.33    4.64 
## 6420600 6441399 6443911 6446289 6452437 6466494 6482325 6490567 6494920 6532006 
##    4.28    3.87    4.85    4.64    4.28    4.54    4.39    4.12    4.41    4.94 
## 6534864 6539118 6545377 6549824 6559872 6576975 6587969 6590034 6612311 6615491 
##    3.65    4.88    4.97    4.34    4.88    4.16    4.65    4.97    4.56    4.59 
## 6634517 6647249 6652304 6654874 6668397 6670256 6671797 6685919 6697145 6711523 
##    4.75    4.12    4.88    4.77    4.74    4.82    4.36    4.72    3.91    4.53 
## 6715739 6716860 6730511 6738530 6749507 6754318 6780617 6781121 6782379 6785090 
##    4.85    4.81    4.52    4.80    4.44    3.64    4.20    4.60    4.57    4.51 
## 6820874 6836001 6850170 6852616 6856709 6861729 6872487 6879846 6880056 6909372 
##    4.23    4.59    4.91    4.60    3.85    4.79    4.99    4.43    4.80    3.94 
## 6912784 6933691 6938117 6967747 6969872 6971786 6975653 6988735 6991328 6992586 
##    4.56    4.74    4.95    4.78    4.72    4.92    4.46    4.79    4.50    4.73
Xmin <- names(Xsum[which(Xsum == min(Xsum))])
Xmin
## [1] "6239179"

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] 0.099740637 0.008232683 0.508368201 0.015766423 1.906818411 0.390605741
## 
## $Xsum
## [1] 2.929532

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 33 32 37 18 66 41
Black 16 35 32 37 17 66 40
X1min <- tbl1 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X1min
##  X-squared 
## 0.09974064

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 119 124
Black 120 123
X2min <- tbl2 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X2min
##   X-squared 
## 0.008232683

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 206 37
Black 205 38
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 21 23 24 29 29 19 21 28 24 25
Black 20 20 21 24 30 25 21 30 25 27
X5min <- tbl5 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X5min
## X-squared 
##  1.906818

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 46 39 16 142
Black 46 44 15 138
X6min <- tbl6 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X6min
## X-squared 
## 0.3906057

Sum of Chi_Squares

Xsum_min <- X1min + X2min + X3min + X4min + X5min + X6min
Xsum_min
## X-squared 
##  2.929532