Data

Search for Best Configuration

M1 <- 8000001
M2 <- 9000000
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 -0.0056  0.0229  0.0057 -0.0029 -0.0020
## X2 -0.0056  1.0000 -0.0021  0.0002 -0.0011 -0.0004
## X3  0.0229 -0.0021  1.0000  0.0018 -0.0025 -0.0033
## X4  0.0057  0.0002  0.0018  1.0000 -0.0032  0.0015
## X5 -0.0029 -0.0011 -0.0025 -0.0032  1.0000 -0.0043
## X6 -0.0020 -0.0004 -0.0033  0.0015 -0.0043  1.0000
names(Xsum) <- M1:M2
Xsum %>%
  summary %>%
  round(2) 
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##    2.92   16.44   20.41   21.05   24.96   65.89
Xsum %>%
  sd %>%
  round(2)
## [1] 6.41
Xsum %>%
  `<=`(5) %>%
  which %>%
  `[`(Xsum, .) %>%
  round(2)
## 8006444 8013324 8013943 8018204 8019602 8021501 8029485 8032117 8046304 8053556 
##    4.71    4.80    4.70    4.72    4.74    4.92    4.47    4.42    4.53    4.42 
## 8061292 8065024 8066550 8075749 8081174 8083928 8093501 8106077 8114427 8123711 
##    4.92    4.52    4.79    4.79    4.95    2.92    4.51    4.17    4.72    3.81 
## 8136733 8186409 8192598 8204726 8205675 8245411 8252434 8259017 8266857 8271860 
##    4.88    4.78    4.83    4.31    4.81    4.73    4.57    3.26    4.10    4.45 
## 8283314 8295631 8297781 8309863 8320135 8325236 8330130 8332972 8350970 8356974 
##    4.87    4.08    4.50    3.59    4.24    3.92    4.90    4.89    4.88    4.98 
## 8370987 8400515 8401527 8411712 8428360 8430096 8441920 8448764 8448839 8453216 
##    4.92    4.26    4.59    4.69    3.97    4.83    3.26    4.91    4.45    4.93 
## 8453472 8458875 8463429 8464487 8470044 8471068 8481836 8499581 8502564 8504261 
##    4.98    4.44    4.90    4.37    3.95    4.36    4.09    4.46    4.32    4.63 
## 8504513 8505249 8524794 8527642 8533327 8555717 8557885 8564589 8566479 8567220 
##    4.80    4.55    4.57    4.64    3.59    3.93    3.97    4.85    4.62    4.90 
## 8571607 8573449 8591853 8598883 8610982 8617081 8629477 8641892 8651195 8652562 
##    4.68    4.19    3.84    4.77    4.79    3.32    4.77    4.45    4.77    4.28 
## 8653777 8662236 8666447 8671591 8673257 8674747 8679902 8694013 8704342 8705234 
##    4.49    4.95    4.90    4.97    3.72    4.74    4.92    4.56    4.55    4.99 
## 8705491 8705843 8708520 8708638 8723945 8726328 8729865 8734986 8782704 8789398 
##    4.35    4.44    4.90    4.27    4.69    4.33    4.83    4.95    4.29    4.82 
## 8791062 8797361 8802716 8810113 8828980 8834705 8843221 8845001 8851236 8865961 
##    4.29    4.39    4.02    4.82    4.44    4.68    4.72    3.26    4.64    4.81 
## 8872209 8874037 8877882 8910582 8921206 8923526 8923739 8932586 8951449 8964885 
##    3.97    3.76    4.52    4.01    4.15    4.76    4.38    4.91    4.27    4.87 
## 8966481 8966829 8972973 8974977 8976946 8980161 8989203 8999798 
##    4.84    4.52    4.80    4.56    4.63    4.95    3.54    4.35
Xmin <- names(Xsum[which(Xsum == min(Xsum))])
Xmin
## [1] "8083928"

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] 0.5748313 0.2058171 0.0000000 0.1418978 0.8399829 1.1536754
## 
## $Xsum
## [1] 2.916205

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 32 39 16 67 40
Black 16 35 32 35 19 65 41
X1min <- tbl1 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X1min
## X-squared 
## 0.5748313

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 122 121
Black 117 126
X2min <- tbl2 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X2min
## X-squared 
## 0.2058171

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 22 22 23 28 28 22 21 28 23 26
Black 19 21 22 25 31 22 21 30 26 26
X5min <- tbl5 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X5min
## X-squared 
## 0.8399829

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 44 38 16 145
Black 48 45 15 135
X6min <- tbl6 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X6min
## X-squared 
##  1.153675

Sum of Chi_Squares

Xsum_min <- X1min + X2min + X3min + X4min + X5min + X6min
Xsum_min
## X-squared 
##  2.916205