You think that approximately 25% of the members of a certain population smoke, but you want to take a sample in order to make an estimate. You want the standard error of  to be no greater than 0.06.
(a) Using 0.25 as your guess of , how large does your sample need to be?
(b) Suppose you have no guess for . How large does your sample need to be so that the SE is no greater than 0.06 no matter what  is?