# 2005 年 06 月 07 日作成
# number of population
no.pop<-10000
# number of repeated sample
no.rep<-1000
# sample size
no.sample<-10
# population of normal
x<-round(rnorm(no.pop,70,7))
# parameter of population distribution
mean(x);median(x);sd(x);var(x)
xbar<-rep(0,no.rep)
xmedian<-rep(0,no.rep)
for(i in 1:no.rep){
r<-trunc(runif(no.sample)*no.pop)+1
xbar[i]<-mean(x[r])
xmedian[i]<-median(x[r])
}
# plotting population density
plot(density(x),xlim=c(40,100),ylim=c(0,0.20))
par(new=T)
# plotting sample distribution of sample mean
plot(density(xbar),xlim=c(40,100),ylim=c(0,0.20))
par(new=T)
# plotting sample distribution of sample median
plot(density(xmedian),xlim=c(40,100),ylim=c(0,0.20))