# Simulate the distribution of the error in the sample mean as an
# estimate of the population mean, for iid data from a specified
# distribution.
#
# The arguments are the sample size (n), the number of replications to
# use in simulating the distribution of error (rep), the function for
# generating random values (gen), which takes the sample size as its
# sole argument, and finally the true mean (true_mean) of the
# distribution.
#
# The value returned is a sample (of size rep) of the errors in
# estimating the mean.
mean_sim <- function (n, rep, gen, true_mean)
{
errors <- numeric(rep)
for (i in 1:rep) {
samp <- gen(n)
errors[i] <- mean(samp) - true_mean
}
errors
}