# 2005 年 06 月 07 日作成
# number of repeated sample
no.rep<-1000
# sample size
no.sample<-5
# population of mixed normals
x1<-round(rnorm(700,70,7))
x2<-round(rnorm(300,40,8))
x<-c(x1,x2)
x<-c(x1,x2)
# 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)*1000)+1
xbar[i]<-mean(x[r])
xmedian[i]<-median(x[r])
}
# plotting population density
plot(density(x),xlim=c(0,100),ylim=c(0,0.1))
par(new=T)
# plotting sample distribution of sample mean
plot(density(xbar),xlim=c(0,100),ylim=c(0,0.1))
par(new=T)
# plotting sample distribution of sample median
plot(density(xmedian),xlim=c(0,100),ylim=c(0,0.1))