# create an empty variable called sample.data
sample.data = NA

# create an empty variable called sample.means
sample.means = NA

# create an empty variable called sample.vars
sample.vars = NA

# this is a structure called a for loop. it loops through the commands between
# the brackets {} as many times are specified.
# in this case, the first command makes a random sample of data, sample.data
# that has 5 values, a mean of 300, and a standard deviation of 25
# it then makes the mean of the sample, and stores it in sample.means
# when the loop is done there will be 1000 means of 1000 samples.
# the same thing is done for variance.
for (counter in 1:1000)
{
  sample.data = rnorm(5,300,25)
  sample.means[counter] = mean(sample.data)
  sample.vars[counter] = var(sample.data)
}

# set up a side by side plot
par(mfrow=c(2, 2))
par(mar=c(1,1,1,1))

# plot the sample means
plot(sample.means,ylim = c(275,325))
# histogram the sample means
hist(sample.means)
# plot the sample variances
plot(sample.vars,ylim = c(1,2000))
# histogramt the sample variances
hist(sample.vars)