Data

Search for Best Configuration

M1 <- 2000001
M2 <- 3000000
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 -0.0035  0.0222  0.0045 -0.0022 -0.0056
## X2 -0.0035  1.0000 -0.0028  0.0017 -0.0032 -0.0001
## X3  0.0222 -0.0028  1.0000  0.0033 -0.0016 -0.0037
## X4  0.0045  0.0017  0.0033  1.0000 -0.0046  0.0022
## X5 -0.0022 -0.0032 -0.0016 -0.0046  1.0000 -0.0034
## X6 -0.0056 -0.0001 -0.0037  0.0022 -0.0034  1.0000
names(Xsum) <- M1:M2
Xsum %>%
  summary %>%
  round(2) 
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##    3.28   16.43   20.41   21.04   24.95   61.79
Xsum %>%
  sd %>%
  round(2)
## [1] 6.42
Xsum %>%
  `<=`(5) %>%
  which %>%
  `[`(Xsum, .) %>%
  round(2)
## 2007659 2016250 2021405 2022872 2025782 2032480 2032952 2045821 2062154 2071267 
##    4.85    4.06    4.75    4.58    3.61    4.33    5.00    4.89    4.72    4.33 
## 2092702 2101855 2117533 2128211 2133695 2144706 2150503 2158765 2167082 2174910 
##    4.56    4.64    4.72    4.79    4.60    4.21    4.70    4.86    5.00    4.72 
## 2175349 2181871 2184510 2188837 2228259 2228979 2237708 2243169 2255821 2263311 
##    3.76    4.79    4.57    3.83    3.48    4.15    3.78    4.69    4.75    4.74 
## 2275172 2278878 2289582 2302608 2351392 2354106 2360956 2370359 2374812 2377544 
##    4.80    4.83    4.38    3.70    4.49    4.38    3.76    4.97    4.53    4.92 
## 2387771 2392338 2405555 2414050 2427136 2468470 2484005 2504268 2506035 2510677 
##    4.89    4.27    3.75    4.36    4.37    4.73    4.67    4.63    4.69    4.75 
## 2518096 2523005 2536412 2537043 2540550 2551791 2555280 2571434 2578130 2580564 
##    4.47    4.60    4.93    4.59    3.42    4.48    4.72    4.65    4.86    4.17 
## 2616984 2631517 2633308 2666333 2668740 2669867 2670036 2674190 2685704 2695794 
##    4.19    4.68    4.30    3.49    4.94    4.94    4.97    3.28    4.07    4.54 
## 2701924 2706817 2710241 2716673 2725843 2739162 2740753 2746634 2752347 2756708 
##    4.44    4.82    4.94    4.86    4.66    4.74    4.56    4.04    4.75    4.27 
## 2770257 2782756 2782973 2794838 2825281 2826824 2836739 2848839 2854173 2869921 
##    4.80    4.95    3.71    4.55    4.59    3.82    4.14    4.90    3.99    4.89 
## 2888945 2900261 2910370 2922902 2927655 2939288 2962610 2996913 2998907 
##    4.01    4.11    4.87    4.97    4.41    4.72    4.39    4.91    4.63
Xmin <- names(Xsum[which(Xsum == min(Xsum))])
Xmin
## [1] "2674190"

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] 0.616530711 0.008232683 0.000000000 0.015766423 2.278199212 0.360134749
## 
## $Xsum
## [1] 3.278864

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 15 36 31 36 17 66 42
Black 17 32 33 38 18 66 39
X1min <- tbl1 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X1min
## X-squared 
## 0.6165307

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 206 37
Black 205 38
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 22 22 22 29 27 20 19 31 24 27
Black 19 21 23 24 32 24 23 27 25 25
X5min <- tbl5 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X5min
## X-squared 
##  2.278199

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 45 42 17 139
Black 47 41 14 141
X6min <- tbl6 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X6min
## X-squared 
## 0.3601347

Sum of Chi_Squares

Xsum_min <- X1min + X2min + X3min + X4min + X5min + X6min
Xsum_min
## X-squared 
##  3.278864