# 2005 年 06 月 21 日作成
# number of repeated sample
no.rep<-5000
# function of sampling median from population with sample size no.sample
sampling<-function(no.sample=5) rnorm(no.sample,0,1)
# calculation mean and median
sample.variance<-function(x)sum((x-mean(x))**2)
# defining objects to store results
res<-rep(0,no.rep)
for (i in 1:no.rep) res[i]<-sample.variance(sampling())
plot(density(res),col=1,xlim=c(0,10),ylim=c(0,0.3),type="l",main="", 
xlab="sampling distribution of median for n = 5, 25, 100")
#lines(density(res[,1]),col=3)
x<-seq(0,10,by=0.01)
par(new=T)
plot(x,dchisq(x,4),col=2,xlim=c(0,10),ylim=c(0,0.3),type="l")