#  2004 年 12 月 07 日作成
# number of repitation
num.rep<-200000
# number of sample
num.sam<-20
s<-rep(0,num.rep)
for (i in 1:num.sam){
s<-s+runif(num.rep,0,1)
}
s<-s/num.sam
s<-sqrt(num.sam)*(s-1/2)/sqrt(1/12)
plot(density(s),xlim=c(-4,4),ylim=c(0,0.5),type="l")
par(new=T)
y<-seq(-4,4,by=0.001)
par(new=T)
plot(y,dnorm(y,0,1),xlim=c(-4,4),ylim=c(0,0.5),type="l")