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  0.0015  0.0358 -0.0021  0.0034 -0.0032
## X2  0.0015  1.0000 -0.0005 -0.0002  0.0013 -0.0015
## X3  0.0358 -0.0005  1.0000 -0.0007  0.0060  0.0004
## X4 -0.0021 -0.0002 -0.0007  1.0000 -0.0016 -0.0027
## X5  0.0034  0.0013  0.0060 -0.0016  1.0000  0.0005
## X6 -0.0032 -0.0015  0.0004 -0.0027  0.0005  1.0000
names(Xsum) <- M1:M2
Xsum %>%
  summary %>%
  round(2) 
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##    2.75   16.37   20.35   21.02   24.96   73.47
Xsum %>%
  sd %>%
  round(2)
## [1] 6.48
Xsum %>%
  `<=`(5) %>%
  which %>%
  `[`(Xsum, .) %>%
  round(2)
## 4018499 4034338 4037125 4055381 4058905 4059328 4061129 4067309 4094797 4118540 
##    4.15    4.27    4.65    4.56    4.56    4.78    3.81    4.41    4.64    4.68 
## 4120734 4123753 4140799 4142316 4147439 4154356 4155151 4155576 4157276 4171179 
##    4.17    4.26    4.77    4.96    4.62    4.67    4.78    4.13    4.68    4.89 
## 4179741 4181367 4195506 4197270 4209891 4231607 4241357 4270705 4272530 4281439 
##    3.76    4.66    4.81    4.40    4.88    4.84    4.74    5.00    4.52    4.96 
## 4296505 4298835 4298950 4311409 4320478 4322908 4328182 4329849 4356093 4394139 
##    4.56    4.60    4.22    4.72    4.30    4.62    4.54    4.24    4.84    4.80 
## 4412209 4431185 4433304 4442647 4444451 4446717 4454780 4460208 4488852 4489900 
##    4.67    4.10    4.96    4.97    4.61    4.17    2.75    4.52    4.67    4.96 
## 4496431 4504497 4508289 4517167 4527151 4532579 4541949 4543753 4560837 4561852 
##    4.89    4.60    3.66    4.75    4.64    4.03    4.20    4.52    4.73    4.59 
## 4564999 4570374 4585807 4594013 4594553 4596628 4602708 4608858 4647992 4653701 
##    4.82    4.83    4.56    4.62    4.61    4.82    4.21    4.83    4.08    4.89 
## 4661126 4694564 4705552 4706622 4714892 4727053 4732441 4735991 4747739 4752614 
##    4.85    4.99    3.85    4.35    4.40    4.36    4.45    4.94    4.37    4.79 
## 4762474 4769661 4770735 4777286 4778699 4779458 4784860 4786335 4825582 4826093 
##    4.97    4.95    4.80    4.94    4.67    4.11    4.17    4.77    4.73    3.80 
## 4847256 4849866 4851395 4881358 4892565 4893374 4893451 4900962 4906951 4918638 
##    4.55    3.91    4.69    4.06    4.13    4.12    4.71    4.34    4.71    4.80 
## 4925010 4926287 4926453 4930439 4943169 4945510 4961083 4962241 4969147 4976671 
##    4.58    4.04    4.88    4.52    3.92    4.64    4.77    4.80    4.99    4.52 
## 4982207 4982821 4996367 
##    4.22    4.78    4.46
Xmin <- names(Xsum[which(Xsum == min(Xsum))])
Xmin
## [1] "4454780"

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] 0.8299960 0.0584915 0.2954436 0.1941533 0.8463114 0.5219614
## 
## $Xsum
## [1] 2.746357

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 19 26 27 54 20 50 112
Black 18 32 28 54 18 48 110
X1min <- tbl1 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X1min
## X-squared 
##  0.829996

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 148 160
Black 151 157
X2min <- tbl2 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X2min
## X-squared 
## 0.0584915

학적 상태

tbl3 <- class_roll$status %>%
  table(class_roll$group, .) 
tbl3 %>%
  pander
  학생 휴학
Red 276 32
Black 280 28
X3min <- tbl3 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X3min
## X-squared 
## 0.2954436

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 257 51
Black 261 47
X4min <- tbl4 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X4min
## X-squared 
## 0.1941533

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 34 28 25 33 25 38 38 33
Black 23 32 34 25 26 31 30 36 38 33
X5min <- tbl5 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X5min
## X-squared 
## 0.8463114

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 67 48 23 170
Black 61 47 26 174
X6min <- tbl6 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X6min
## X-squared 
## 0.5219614

Sum of Chi_Squares

Xsum_min <- X1min + X2min + X3min + X4min + X5min + X6min
Xsum_min
## X-squared 
##  2.746357