d=read.table("http://www.stat.sc.edu/~hansont/stat205/height_2014.txt",header=F)
d=c(70,70,72,63,60,60,72,67,65,67,68,62,64,69,65,63,66,69,66,72,64,69,63,73,68
68,68,65,64,65,76,76,66,63,65,66,67,68,67,73,72,71,62,63,69,72,63,60,61,75
72,68,72,64,64,60,72,68,61,71,64,68,69,64,67,65,76,75,68,66,67,65,62,71,67
63,66,66,69,70,62,67,68,67,62,72,62,61,68,69,63,62)

h=d[,2]*12+d[,3] # height in inches
m=length(h)      # population size
n=5              # sample size

# compute one mean of size n=5
ybar=0
for(j in 1:n){
 index=ceiling(runif(1)*m)
 cat("Student",index,"has height",h[index],"inches. \n")
 ybar=ybar+h[index]}
cat("Mean of all",n,"is ybar =",ybar/n,"inches. \n")

# make histogram of 1000 sample ybar's, each n=5
total=1000
mu=mean(h)
means=rep(0,total)
for(i in 1:total){
 ybar=0
 for(j in 1:n){ybar=ybar+h[ceiling(runif(1)*m)]}
 ybar=ybar/n
 means[i]=ybar
}

par(mfrow=c(2,1))
hist(h,freq=FALSE,xlim=c(min(h),max(h)),main="Population density")
hist(means,freq=FALSE,xlim=c(min(h),max(h)),main="Density of ybar for n=5")