confidence-interval-proportion (x n confidence)
Suppose we have a sample of n' things and x' of them are successes.'' We
can estimate the population proportion of successes as x/n; call it p-hat.'<br> This function computes the estimate and a confidence interval on it. This<br> function is not appropriate for small samples with p-hat far from 1/2: x'
should be at least 5, and so should n'- x.' This function returns three values:
p-hat, and the lower and upper bounds of the confidence interval. `Confidence'
should be a number between 0 and 1, exclusive.