Data

Search for Best Configuration

M1 <- 7000001
M2 <- 8000000
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  0.0015  0.0364 -0.0032  0.0042 -0.0022
## X2  0.0015  1.0000 -0.0004 -0.0001  0.0000 -0.0009
## X3  0.0364 -0.0004  1.0000 -0.0006  0.0062 -0.0003
## X4 -0.0032 -0.0001 -0.0006  1.0000 -0.0015 -0.0011
## X5  0.0042  0.0000  0.0062 -0.0015  1.0000  0.0001
## X6 -0.0022 -0.0009 -0.0003 -0.0011  0.0001  1.0000
names(Xsum) <- M1:M2
Xsum %>%
  summary %>%
  round(2) 
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##    3.29   16.37   20.37   21.03   24.97   68.54
Xsum %>%
  sd %>%
  round(2)
## [1] 6.48
Xsum %>%
  `<=`(5) %>%
  which %>%
  `[`(Xsum, .) %>%
  round(2)
## 7001897 7007295 7016007 7018751 7028465 7036556 7040385 7046325 7052294 7063143 
##    4.11    3.68    3.29    3.96    4.99    4.85    4.89    3.78    4.30    4.52 
## 7066097 7097457 7100424 7122358 7124267 7155678 7156277 7159153 7175166 7185541 
##    4.91    4.56    4.74    4.51    4.30    3.98    4.40    4.06    4.25    4.98 
## 7195466 7216419 7217377 7220169 7226189 7241419 7247978 7248408 7250395 7250929 
##    4.68    3.87    4.71    4.19    4.93    4.60    4.91    4.90    4.84    3.67 
## 7257060 7264044 7265783 7275829 7281746 7281938 7295444 7309325 7319419 7343051 
##    4.88    3.91    4.59    4.28    4.53    3.73    4.48    4.73    4.72    4.83 
## 7361623 7362088 7363384 7377292 7380324 7383493 7398096 7403092 7406321 7419271 
##    4.79    4.18    4.42    4.50    4.97    4.11    4.43    4.63    3.93    4.61 
## 7426356 7426376 7448115 7448946 7449419 7475224 7480500 7484906 7499362 7501030 
##    4.39    4.80    4.89    4.41    4.97    4.88    4.84    4.91    4.40    4.82 
## 7505882 7524146 7528452 7531381 7539998 7546797 7553447 7565689 7574402 7579552 
##    4.72    3.89    3.45    4.27    4.48    4.91    4.99    4.09    4.09    4.73 
## 7586277 7588916 7593923 7598403 7601841 7609208 7610956 7615691 7628382 7629216 
##    4.37    3.98    4.82    4.59    4.83    4.67    4.45    3.37    4.89    4.85 
## 7629996 7630864 7632123 7636254 7636500 7659236 7676801 7682850 7683553 7694763 
##    4.52    4.78    4.66    4.19    4.01    4.96    5.00    4.79    4.43    4.96 
## 7698425 7712630 7712761 7728206 7732958 7736198 7737312 7739188 7741781 7754083 
##    3.62    4.97    3.65    4.22    4.21    3.97    4.88    3.98    4.28    4.34 
## 7765662 7778397 7786906 7797080 7798837 7800157 7801558 7823709 7831581 7838055 
##    4.31    4.69    4.26    4.44    4.72    4.51    4.68    4.49    4.60    4.93 
## 7843566 7854665 7856250 7856262 7857664 7863127 7869656 7898916 7899148 7918418 
##    4.87    4.94    4.77    4.40    4.77    4.24    4.90    4.61    4.21    4.36 
## 7918534 7932515 7935441 7940954 7950287 7956601 7958504 7958879 7963570 7973609 
##    4.93    4.91    4.12    3.94    4.31    4.30    4.34    4.54    3.49    3.95 
## 7976029 7983861 7989776 
##    4.28    4.67    4.66
Xmin <- names(Xsum[which(Xsum == min(Xsum))])
Xmin
## [1] "7016007"

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] 1.07734302 0.16247639 0.00000000 0.04853833 0.99601651 1.01050945
## 
## $Xsum
## [1] 3.294884

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 21 29 27 52 19 51 109
Black 16 29 28 56 19 47 113
X1min <- tbl1 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X1min
## X-squared 
##  1.077343

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 147 161
Black 152 156
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 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 30 37 26 24 32 28 36 37 34
Black 23 32 31 27 27 32 27 38 39 32
X5min <- tbl5 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X5min
## X-squared 
## 0.9960165

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 51 23 168
Black 62 44 26 176
X6min <- tbl6 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X6min
## X-squared 
##  1.010509

Sum of Chi_Squares

Xsum_min <- X1min + X2min + X3min + X4min + X5min + X6min
Xsum_min
## X-squared 
##  3.294884