Data

Search for Best Configuration

M1 <- 1000001
M2 <- 2000000
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  0.0362 -0.0023  0.0044 -0.0015
## X2  0.0036  1.0000 -0.0014  0.0006  0.0007  0.0000
## X3  0.0362 -0.0014  1.0000 -0.0007  0.0053  0.0003
## X4 -0.0023  0.0006 -0.0007  1.0000 -0.0010 -0.0015
## X5  0.0044  0.0007  0.0053 -0.0010  1.0000  0.0002
## X6 -0.0015  0.0000  0.0003 -0.0015  0.0002  1.0000
names(Xsum) <- M1:M2
Xsum %>%
  summary %>%
  round(2) 
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##    2.93   16.38   20.38   21.04   24.98   70.07
Xsum %>%
  sd %>%
  round(2)
## [1] 6.49
Xsum %>%
  `<=`(5) %>%
  which %>%
  `[`(Xsum, .) %>%
  round(2)
## 1001139 1008696 1009858 1011534 1015981 1016532 1021738 1022941 1035569 1044040 
##    4.78    4.85    4.58    3.51    4.99    4.75    4.38    4.32    4.54    4.67 
## 1046296 1052086 1065283 1068872 1080835 1081410 1086498 1106284 1114904 1119765 
##    4.96    4.95    4.70    3.47    4.90    4.81    4.96    4.96    4.89    4.81 
## 1128852 1132146 1160629 1162117 1163546 1190415 1192311 1206690 1210439 1213532 
##    4.49    4.49    3.82    4.51    4.58    4.54    4.17    4.98    4.57    4.48 
## 1219315 1223167 1234419 1238027 1254511 1257750 1260601 1261903 1263390 1263954 
##    4.49    4.99    3.13    4.89    4.31    3.72    4.36    4.80    4.69    4.88 
## 1269014 1277153 1283620 1294506 1299762 1303196 1308076 1310064 1315777 1320685 
##    4.37    4.68    3.56    4.74    4.70    4.69    4.94    4.64    4.70    4.70 
## 1322839 1340258 1343173 1347185 1374904 1383657 1386417 1387639 1406441 1415341 
##    4.29    3.32    4.81    4.84    4.78    3.16    4.79    4.60    4.78    4.84 
## 1416778 1430962 1437591 1452458 1453088 1455857 1463696 1476804 1479341 1487865 
##    4.33    4.96    4.36    4.17    4.89    3.98    4.25    4.71    4.83    4.24 
## 1495089 1508636 1518001 1531259 1532619 1539451 1540974 1569435 1575316 1575965 
##    3.58    4.89    3.93    4.29    4.14    4.93    4.84    4.11    4.83    5.00 
## 1592291 1594482 1600085 1603176 1604479 1611235 1621200 1624775 1635499 1664923 
##    4.29    3.49    4.95    4.26    4.99    4.10    4.04    3.79    4.01    4.82 
## 1667557 1675782 1698802 1711374 1711702 1716032 1722791 1762626 1778234 1790767 
##    4.61    4.27    4.78    4.59    3.86    4.95    4.60    4.12    4.60    4.05 
## 1792086 1792331 1793554 1798466 1803518 1821708 1835875 1838593 1844216 1857490 
##    4.87    4.83    4.31    3.97    4.97    4.71    2.93    4.89    4.33    4.23 
## 1859958 1861424 1862177 1870509 1871528 1886229 1891255 1892600 1900106 1901396 
##    4.53    4.08    4.92    4.12    4.67    4.52    4.41    4.95    4.99    4.76 
## 1908412 1908915 1913308 1919183 1923725 1930878 1931947 1937684 1941614 1948506 
##    5.00    4.83    4.91    4.87    4.72    4.77    4.28    4.64    4.76    4.78 
## 1948604 1964003 1964221 1968129 1976106 1982999 1995103 
##    4.73    4.87    4.31    4.73    4.69    4.87    4.11
Xmin <- names(Xsum[which(Xsum == min(Xsum))])
Xmin
## [1] "1835875"

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] 1.01247976 0.05849150 0.00000000 0.04853833 1.35934104 0.44992194
## 
## $Xsum
## [1] 2.928773

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 30 27 52 21 48 113
Black 20 28 28 56 17 50 109
X1min <- tbl1 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X1min
## X-squared 
##   1.01248

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 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 22 31 33 25 24 34 29 36 39 35
Black 25 31 35 28 27 30 26 38 37 31
X5min <- tbl5 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X5min
## X-squared 
##  1.359341

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 62 49 23 174
Black 66 46 26 170
X6min <- tbl6 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X6min
## X-squared 
## 0.4499219

Sum of Chi_Squares

Xsum_min <- X1min + X2min + X3min + X4min + X5min + X6min
Xsum_min
## X-squared 
##  2.928773