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  0.0018  0.0370 -0.0024  0.0040 -0.0026
## X2  0.0018  1.0000 -0.0017  0.0005  0.0013 -0.0012
## X3  0.0370 -0.0017  1.0000 -0.0002  0.0046 -0.0017
## X4 -0.0024  0.0005 -0.0002  1.0000 -0.0032 -0.0017
## X5  0.0040  0.0013  0.0046 -0.0032  1.0000 -0.0002
## X6 -0.0026 -0.0012 -0.0017 -0.0017 -0.0002  1.0000
names(Xsum) <- M1:M2
Xsum %>%
  summary %>%
  round(2) 
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##    3.20   16.37   20.36   21.03   24.96   81.95
Xsum %>%
  sd %>%
  round(2)
## [1] 6.48
Xsum %>%
  `<=`(5) %>%
  which %>%
  `[`(Xsum, .) %>%
  round(2)
## 2007385 2010019 2018140 2029947 2032987 2034427 2034654 2037798 2048523 2048589 
##    4.56    4.37    4.59    4.99    4.86    4.41    4.74    4.74    3.22    3.23 
## 2064016 2089514 2112278 2120324 2130097 2131879 2134999 2137627 2155732 2157468 
##    4.86    4.68    4.55    4.12    4.71    4.43    4.91    4.85    3.84    4.61 
## 2175587 2175893 2182941 2184316 2192613 2221709 2226365 2231106 2267711 2273209 
##    4.94    4.83    4.90    4.72    4.10    4.59    4.07    4.18    3.97    4.43 
## 2283356 2287104 2303940 2314723 2318954 2325332 2325627 2329325 2333767 2338593 
##    4.58    4.04    4.76    3.76    5.00    4.48    3.85    4.64    4.70    4.16 
## 2344586 2350396 2358594 2359572 2363473 2365802 2366943 2387429 2398722 2408037 
##    4.92    4.64    4.67    3.90    4.99    4.82    4.74    4.06    4.60    3.97 
## 2428478 2437840 2457807 2461629 2473855 2478202 2484458 2484810 2493645 2498667 
##    4.75    3.59    4.64    3.94    4.75    4.66    3.82    4.43    4.28    4.79 
## 2501829 2510777 2511151 2522696 2529744 2533909 2541129 2558244 2572873 2573656 
##    4.75    4.71    4.59    4.72    4.70    3.88    4.61    4.42    3.20    4.02 
## 2596829 2608182 2609660 2610544 2626559 2639214 2639931 2645345 2648376 2652219 
##    4.91    4.42    4.85    4.82    4.67    4.55    3.60    4.80    4.94    4.84 
## 2656432 2660194 2672270 2678320 2682465 2687714 2688697 2697187 2700475 2717666 
##    4.78    4.68    3.69    4.52    4.60    4.69    4.61    4.77    4.66    4.61 
## 2718138 2719199 2745293 2747589 2749748 2752844 2767654 2778712 2791372 2815296 
##    5.00    3.91    4.73    4.55    4.44    4.60    3.91    4.89    4.60    4.98 
## 2816410 2817519 2820680 2850767 2857819 2858775 2865359 2865820 2868185 2886002 
##    3.42    4.12    4.35    3.46    3.72    4.88    4.93    4.53    4.36    4.00 
## 2894202 2894259 2895425 2910850 2913078 2915848 2917250 2928599 2929759 2934676 
##    4.86    4.83    4.88    4.62    4.68    4.48    4.17    4.35    3.90    4.23 
## 2934998 2935516 2942404 2944211 2951829 2953794 2957268 2961019 2979331 
##    4.52    4.29    4.74    4.62    4.63    4.87    4.63    4.85    4.28
Xmin <- names(Xsum[which(Xsum == min(Xsum))])
Xmin
## [1] "2572873"

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] 1.95408477 0.05849150 0.07386091 0.04853833 0.95977579 0.10869611
## 
## $Xsum
## [1] 3.203447

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 23 54 19 52 112
Black 19 28 32 54 19 46 110
X1min <- tbl1 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X1min
## X-squared 
##  1.954085

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 151 157
Black 148 160
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 279 29
Black 277 31
X3min <- tbl3 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X3min
##  X-squared 
## 0.07386091

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 258 50
Black 260 48
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 24 31 33 27 27 31 30 36 37 32
Black 23 31 35 26 24 33 25 38 39 34
X5min <- tbl5 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X5min
## X-squared 
## 0.9597758

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 65 48 25 170
Black 63 47 24 174
X6min <- tbl6 %>%
  chisq.test(simulate.p.value = TRUE) %>%
  `[[`(1)
X6min
## X-squared 
## 0.1086961

Sum of Chi_Squares

Xsum_min <- X1min + X2min + X3min + X4min + X5min + X6min
Xsum_min
## X-squared 
##  3.203447