Data

Search for Best Configuration

M1 <- 9000001
M2 <- 10000000
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  0.0011  0.0353 -0.0021  0.0032 -0.0027
## X2  0.0011  1.0000 -0.0004  0.0007  0.0010 -0.0008
## X3  0.0353 -0.0004  1.0000 -0.0010  0.0062 -0.0022
## X4 -0.0021  0.0007 -0.0010  1.0000  0.0011 -0.0005
## X5  0.0032  0.0010  0.0062  0.0011  1.0000 -0.0009
## X6 -0.0027 -0.0008 -0.0022 -0.0005 -0.0009  1.0000
names(Xsum) <- M1:M2
Xsum %>%
  summary %>%
  round(2) 
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##    2.34   16.38   20.38   21.04   24.98   66.49
Xsum %>%
  sd %>%
  round(2)
## [1] 6.48
Xsum %>%
  `<=`(5) %>%
  which %>%
  `[`(Xsum, .) %>%
  round(2)
## 9004550 9006036 9008004 9049385 9051597 9055258 9060045 9066328 9086945 9087632 
##    3.56    4.11    4.58    4.25    4.97    4.69    3.47    4.77    3.12    4.39 
## 9126786 9129440 9147559 9149022 9155587 9161880 9169073 9183054 9189275 9191999 
##    4.57    4.91    4.86    4.28    4.53    4.41    4.54    4.46    4.54    3.83 
## 9194037 9204814 9216219 9227144 9231080 9232276 9235891 9244316 9260059 9272112 
##    4.54    4.24    4.50    4.30    4.61    4.77    4.97    4.34    4.86    3.72 
## 9276102 9280888 9282555 9287413 9288367 9296513 9298885 9300632 9320426 9320665 
##    4.59    4.57    4.36    5.00    4.60    4.30    4.42    4.86    3.32    4.61 
## 9320949 9321445 9323891 9325674 9331113 9345564 9346300 9348106 9357961 9363416 
##    4.17    4.82    4.27    4.19    3.68    3.46    4.99    4.70    4.26    4.77 
## 9371623 9385067 9408353 9409708 9413846 9420824 9427335 9446059 9448619 9450268 
##    4.63    4.86    4.63    4.16    4.72    4.16    4.29    3.98    4.68    4.82 
## 9455775 9458647 9461929 9462104 9464090 9470896 9475772 9477554 9503891 9505479 
##    3.64    4.16    3.60    4.63    4.23    4.86    4.52    4.51    4.47    4.32 
## 9506114 9507581 9509850 9519512 9534066 9545849 9550017 9555093 9560342 9575275 
##    4.87    4.81    2.86    4.98    4.92    3.99    4.91    4.28    4.27    4.36 
## 9587532 9588140 9592579 9594925 9597048 9600625 9609256 9613187 9618240 9619122 
##    4.74    4.65    3.65    3.63    4.91    4.22    4.57    3.33    4.91    4.84 
## 9621079 9635128 9650561 9660455 9669679 9671888 9680589 9688007 9692527 9724274 
##    4.45    4.21    3.68    4.92    4.95    4.46    4.61    4.90    2.34    3.36 
## 9728074 9728820 9752358 9753699 9756383 9765307 9777651 9785292 9794812 9800248 
##    4.30    4.88    4.53    4.67    4.62    3.68    4.51    4.88    4.89    4.88 
## 9835324 9845294 9847018 9848432 9856776 9859622 9876821 9877515 9882820 9888746 
##    5.00    4.93    4.74    4.41    3.35    4.17    4.39    4.59    4.89    4.58 
## 9897881 9922114 9933378 9948282 9959322 9986797 9989660 9991941 
##    4.54    4.49    4.58    4.69    3.54    4.03    4.92    3.95
Xmin <- names(Xsum[which(Xsum == min(Xsum))])
Xmin
## [1] "9692527"

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] 0.331700980 0.006499056 0.000000000 0.436845008 1.211770077 0.356171939
## 
## $Xsum
## [1] 2.342987

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 18 30 29 54 19 49 109
Black 19 28 26 54 19 49 113
X1min <- tbl1 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X1min
## X-squared 
##  0.331701

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 150 158
Black 149 159
X2min <- tbl2 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X2min
##   X-squared 
## 0.006499056

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 262 46
Black 256 52
X4min <- tbl4 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X4min
## X-squared 
##  0.436845

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 25 28 35 27 24 32 28 38 39 32
Black 22 34 33 26 27 32 27 36 37 34
X5min <- tbl5 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X5min
## X-squared 
##   1.21177

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 63 49 26 170
Black 65 46 23 174
X6min <- tbl6 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X6min
## X-squared 
## 0.3561719

Sum of Chi_Squares

Xsum_min <- X1min + X2min + X3min + X4min + X5min + X6min
Xsum_min
## X-squared 
##  2.342987