Data

Search for Best Configuration

M1 <- 8000001
M2 <- 9000000
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  0.0017  0.0371 -0.0015  0.0058  0.0000
## X2  0.0017  1.0000  0.0015  0.0010  0.0009 -0.0007
## X3  0.0371  0.0015  1.0000  0.0015  0.0040 -0.0014
## X4 -0.0015  0.0010  0.0015  1.0000 -0.0008 -0.0015
## X5  0.0058  0.0009  0.0040 -0.0008  1.0000  0.0029
## X6  0.0000 -0.0007 -0.0014 -0.0015  0.0029  1.0000
names(Xsum) <- M1:M2
Xsum %>%
  summary %>%
  round(2) 
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##    3.11   16.36   20.37   21.03   24.98   67.20
Xsum %>%
  sd %>%
  round(2)
## [1] 6.49
Xsum %>%
  `<=`(5) %>%
  which %>%
  `[`(Xsum, .) %>%
  round(2)
## 8004008 8005274 8015739 8018442 8025560 8032634 8036007 8040952 8044219 8046181 
##    4.42    3.87    4.34    4.66    4.70    3.80    4.95    4.83    4.43    4.71 
## 8050012 8051126 8052702 8059434 8060891 8061366 8071930 8075772 8077719 8078025 
##    4.95    4.77    3.15    4.92    4.26    4.87    4.87    4.83    4.99    4.63 
## 8083613 8094831 8103098 8106074 8113128 8123981 8148906 8151868 8152335 8152857 
##    4.27    4.94    4.84    4.26    3.97    3.61    4.75    3.62    3.66    3.71 
## 8154804 8160640 8180711 8183249 8183729 8187615 8189733 8191104 8201026 8203478 
##    4.99    4.81    3.81    4.82    4.80    3.58    4.96    3.99    4.64    4.42 
## 8206564 8221110 8222064 8222967 8224180 8231010 8244814 8246536 8248375 8249087 
##    4.99    4.75    3.91    4.35    4.94    4.89    4.93    4.74    4.00    4.45 
## 8252031 8262534 8265545 8269419 8291946 8306792 8329650 8329979 8337682 8349409 
##    3.16    4.39    4.44    4.55    4.60    4.64    4.89    4.27    4.43    4.28 
## 8356527 8356974 8383299 8387344 8414548 8416057 8435124 8440477 8442402 8463160 
##    5.00    4.77    4.62    4.67    4.11    4.75    4.82    4.41    5.00    4.62 
## 8477363 8480807 8490587 8500553 8514820 8527678 8529685 8552302 8554633 8561343 
##    4.93    4.96    4.85    4.37    4.96    4.22    3.82    4.53    4.82    4.76 
## 8576113 8576290 8586783 8588273 8588462 8591013 8600878 8613133 8633887 8636365 
##    4.30    4.77    4.16    4.27    4.32    4.54    4.94    4.39    4.92    4.46 
## 8650108 8650277 8652887 8666345 8669889 8671129 8675026 8684555 8711208 8712388 
##    4.30    4.97    3.89    4.75    4.79    4.75    4.96    4.82    4.75    3.11 
## 8712546 8724436 8729699 8759746 8779231 8785502 8799365 8810906 8823626 8836854 
##    4.72    4.82    5.00    4.77    4.77    4.75    4.63    4.25    4.55    3.98 
## 8840019 8855983 8857740 8872535 8875222 8877639 8881643 8887534 8891569 8894687 
##    4.20    4.61    4.59    4.67    4.93    4.97    4.79    4.13    3.23    4.51 
## 8896335 8903272 8913679 8917881 8918268 8920057 8944093 8947430 8949925 8952088 
##    4.50    4.66    4.58    3.61    4.77    4.14    4.49    4.81    4.74    4.79 
## 8963513 8966680 8969854 8974343 8989264 
##    4.14    4.88    4.42    3.92    4.91
Xmin <- names(Xsum[which(Xsum == min(Xsum))])
Xmin
## [1] "8712388"

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] 1.41143575 0.16247639 0.00000000 0.04853833 1.24612600 0.23707769
## 
## $Xsum
## [1] 3.105654

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 29 30 57 18 50 106
Black 19 29 25 51 20 48 116
X1min <- tbl1 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X1min
## X-squared 
##  1.411436

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 35 26 27 33 29 34 38 33
Black 23 33 33 27 24 31 26 40 38 33
X5min <- tbl5 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X5min
## X-squared 
##  1.246126

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 47 23 173
Black 63 48 26 171
X6min <- tbl6 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X6min
## X-squared 
## 0.2370777

Sum of Chi_Squares

Xsum_min <- X1min + X2min + X3min + X4min + X5min + X6min
Xsum_min
## X-squared 
##  3.105654