If you want to be 95 confident of estimating the population

If you want to be 95% confident of estimating the population proportion to within a sampling error of + or - 0.04, what sample size is needed?

Solution

Compute Sample Size ( n ) = n=(Z/E)^2*p*(1-p)
Z a/2 at 0.05 is = 1.96
Samle Proportion = 0.5
ME = 0.04
n = ( 1.96 / 0.04 )^2 * 0.5*0.5
= 600.25 ~ 601