Let there be successes out of Bernoulli Trials. The sample proportion is the fraction of samples which
were successes, so
For large , has an approximately Normal Distribution.
Let RE be the Relative Error and SE the Standard Error, then
where CI is the Confidence Interval and
is the Erf function. The number of tries needed to determine
with Relative Error RE and Confidence Interval CI is
© 1996-9 Eric W. Weisstein