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 -0.0036  0.0206  0.0039 -0.0029 -0.0049
## X2 -0.0036  1.0000 -0.0039  0.0016 -0.0025 -0.0009
## X3  0.0206 -0.0039  1.0000  0.0042 -0.0013 -0.0055
## X4  0.0039  0.0016  0.0042  1.0000 -0.0041  0.0017
## X5 -0.0029 -0.0025 -0.0013 -0.0041  1.0000 -0.0034
## X6 -0.0049 -0.0009 -0.0055  0.0017 -0.0034  1.0000
names(Xsum) <- M1:M2
Xsum %>%
  summary %>%
  round(2) 
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##    2.83   16.45   20.43   21.05   24.97   64.93
Xsum %>%
  sd %>%
  round(2)
## [1] 6.41
Xsum %>%
  `<=`(5) %>%
  which %>%
  `[`(Xsum, .) %>%
  round(2)
## 7003777 7005310 7006261 7035360 7039425 7041563 7055511 7075363 7076071 7086460 
##    4.32    4.73    2.83    4.94    4.06    4.57    4.66    4.68    4.71    4.86 
## 7092874 7110654 7112706 7122439 7125454 7128302 7132278 7153138 7153776 7153990 
##    4.86    5.00    4.84    4.68    4.84    4.44    4.98    4.11    4.35    4.83 
## 7164872 7169998 7179972 7181278 7199354 7203441 7204925 7211838 7214189 7227181 
##    4.44    4.90    3.83    3.93    4.55    4.72    3.98    4.43    4.74    3.80 
## 7233202 7246392 7249477 7260904 7262823 7266448 7271276 7274452 7281704 7281731 
##    4.71    4.53    4.32    4.16    4.41    4.66    4.74    4.85    3.66    4.96 
## 7289417 7290574 7311633 7312194 7316044 7321097 7327825 7342852 7351561 7352786 
##    3.56    4.71    4.11    4.59    4.57    2.87    4.69    4.75    3.23    4.27 
## 7360820 7371823 7374870 7396890 7402727 7411133 7457577 7475400 7509745 7509861 
##    4.94    3.76    4.26    4.71    4.12    4.83    4.02    3.94    4.02    4.25 
## 7520974 7530871 7541978 7548719 7550265 7555696 7556886 7603484 7605059 7616059 
##    3.59    4.99    3.21    4.73    4.38    4.43    4.90    3.86    3.78    4.75 
## 7623709 7627716 7627882 7629134 7630731 7631192 7639628 7649962 7650981 7661529 
##    4.98    4.96    4.56    4.82    4.58    4.46    4.43    4.91    4.80    4.80 
## 7663536 7669978 7677458 7683978 7695065 7696867 7701462 7709894 7718467 7745345 
##    4.68    4.43    3.70    4.41    5.00    4.07    4.05    4.10    4.85    4.90 
## 7747192 7747739 7750077 7759388 7775458 7794076 7811452 7820204 7820374 7829607 
##    4.99    3.86    4.88    4.92    4.81    4.63    4.85    4.78    4.95    4.96 
## 7836934 7842392 7846090 7869674 7873911 7878083 7901898 7904315 7906958 7907744 
##    4.78    4.83    4.81    4.05    4.25    4.68    4.82    4.08    3.28    4.74 
## 7907946 7912319 7918511 7925682 7942471 7959464 7965533 7967335 7968870 7983056 
##    4.91    3.99    4.88    3.88    4.40    4.49    4.86    4.21    4.84    4.84 
## 7983713 7986875 7993104 
##    4.79    3.24    4.92
Xmin <- names(Xsum[which(Xsum == min(Xsum))])
Xmin
## [1] "7006261"

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] 1.00135248 0.40340149 0.00000000 0.01576642 1.21165655 0.19845577
## 
## $Xsum
## [1] 2.830633

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 31 35 17 67 44
Black 16 35 33 39 18 65 37
X1min <- tbl1 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X1min
## X-squared 
##  1.001352

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 116 127
Black 123 120
X2min <- tbl2 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X2min
## X-squared 
## 0.4034015

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 205 38
Black 206 37
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 20 21 22 28 32 20 22 28 24 26
Black 21 22 23 25 27 24 20 30 25 26
X5min <- tbl5 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X5min
## X-squared 
##  1.211657

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 47 40 15 141
Black 45 43 16 139
X6min <- tbl6 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X6min
## X-squared 
## 0.1984558

Sum of Chi_Squares

Xsum_min <- X1min + X2min + X3min + X4min + X5min + X6min
Xsum_min
## X-squared 
##  2.830633