Data

Search for Best Configuration

M1 <- 4000001
M2 <- 5000000
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  0.0206  0.0040 -0.0029 -0.0052
## X2 -0.0026  1.0000 -0.0030  0.0002 -0.0015 -0.0006
## X3  0.0206 -0.0030  1.0000  0.0016 -0.0031 -0.0043
## X4  0.0040  0.0002  0.0016  1.0000 -0.0047  0.0025
## X5 -0.0029 -0.0015 -0.0031 -0.0047  1.0000 -0.0017
## X6 -0.0052 -0.0006 -0.0043  0.0025 -0.0017  1.0000
names(Xsum) <- M1:M2
Xsum %>%
  summary %>%
  round(2) 
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##    2.53   16.43   20.42   21.04   24.97   65.25
Xsum %>%
  sd %>%
  round(2)
## [1] 6.41
Xsum %>%
  `<=`(5) %>%
  which %>%
  `[`(Xsum, .) %>%
  round(2)
## 4022557 4031065 4033502 4051312 4060771 4062173 4064450 4067539 4068983 4070519 
##    4.90    4.94    4.72    4.78    4.98    4.63    4.31    5.00    4.64    4.67 
## 4077278 4085313 4090873 4102216 4137390 4140143 4145247 4146062 4146682 4152711 
##    2.53    4.98    4.05    4.02    4.06    4.80    4.90    4.26    4.89    4.40 
## 4152986 4175507 4176090 4179234 4181032 4182605 4189115 4192542 4194030 4199065 
##    4.85    4.89    4.82    5.00    4.99    4.59    4.86    4.88    4.41    4.05 
## 4213396 4215595 4247406 4261088 4261456 4270605 4283564 4295023 4303224 4312351 
##    4.66    4.79    4.92    4.77    4.92    4.79    4.70    4.95    4.16    4.40 
## 4314520 4317743 4321829 4322333 4333479 4348165 4361801 4366095 4368622 4371381 
##    4.90    4.79    4.51    4.61    4.30    4.71    4.84    4.32    4.12    4.83 
## 4373168 4376269 4384527 4390387 4398367 4399892 4401184 4415681 4422618 4424727 
##    4.72    4.12    4.94    4.26    4.12    4.87    4.44    4.37    4.43    2.96 
## 4426700 4431301 4439186 4446051 4450457 4453161 4460962 4469941 4478388 4497932 
##    4.22    4.93    4.83    4.99    4.47    4.95    4.46    4.66    4.85    4.27 
## 4500871 4506135 4523558 4523619 4537522 4541156 4567278 4583856 4615950 4620012 
##    4.96    4.83    4.96    4.91    4.64    4.82    4.88    4.64    4.59    4.29 
## 4639404 4639820 4658417 4667735 4668603 4676488 4678155 4690792 4702890 4708049 
##    4.73    4.96    4.99    4.45    4.94    4.13    4.65    4.81    4.64    4.33 
## 4710642 4719973 4721228 4729463 4749807 4778328 4790219 4798979 4804771 4816048 
##    4.99    4.05    3.59    4.53    4.94    4.97    3.70    4.93    4.71    4.28 
## 4821575 4830443 4833697 4840946 4847140 4849815 4854582 4857650 4858283 4872952 
##    4.73    4.43    4.85    4.84    4.82    4.17    4.20    4.96    4.70    4.58 
## 4873267 4902398 4906104 4914804 4927967 4929902 4933172 4933174 4937566 4941094 
##    3.52    4.32    4.55    4.81    4.13    4.61    4.83    4.91    4.66    4.13 
## 4987745 4996869 
##    4.86    4.91
Xmin <- names(Xsum[which(Xsum == min(Xsum))])
Xmin
## [1] "4077278"

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] 1.034935859 0.008232683 0.000000000 0.141897810 1.147407411 0.198455775
## 
## $Xsum
## [1] 2.53093

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 17 36 32 35 17 68 38
Black 15 32 32 39 18 64 43
X1min <- tbl1 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X1min
## X-squared 
##  1.034936

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 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 21 22 24 24 28 23 22 28 25 26
Black 20 21 21 29 31 21 20 30 24 26
X5min <- tbl5 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X5min
## X-squared 
##  1.147407

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 
##   2.53093