## Writing Assignment 6: Due Friday, October 31, 2008

Write an essay explaining how a random sample of a fairly small number n
of people can indeed reliably measure the proportions p and 1-p pro or con
on a given issue of a much larger population. Explain why, the smaller
p or 1-p are, the larger the sample size n must be (both to ensure
that the distribution of samples is normal, and to obtain a given margin
of error) but why (other factors being the same) a bigger population
doesn't mean having to take a bigger sample size n. Your essay
should give the reader a feel for how big n must be (so they understand
that n = 1000 for a population of 100 million is very reasonable).
Also be sure to explain what a margin of error of plus or minus 2% actually means and
why a margin of error of plus or minus 2% doesn't guarantee that the sample
measurement is necessarily within 2% of the actual value.