Quiz 5 (10 minutes, 3 points):

Assume a certain large population has a normal distribution with parameters
mu=10, sigma=3. Also, assume the population is homogeneous with respect to
a variable x.  We take 1000 samples (with or without replacement) of size 
100 from this population, in order to find out how precisely we can estimate 
the population mean.  Write code that gives a numerical value for this precision.


#Soln:

xbar = numeric(1000)
for(i in 1:1000)
xbar[i] = mean( rnorm(100,10,3) )
sd(xbar)

# OR 

population = rnorm(1000000,10,3)
xbar = numeric(1000)    
for(i in 1:1000){
sample1 = sample(population, 100, replace=F)
xbar[i] = mean(sample1)
}
sd(xbar)