If you want to be 95​% confident of estimating the population proportion to within a sampling error of ±0.05 and..

Question

If you want to be 95​% confident of estimating the population proportion to within a sampling error of ±0.05 and there is historical evidence that the population proportion is approximately 0.36​, what sample size is​ needed?

A sample size of ______ is needed. (Round up to the nearest​ integer.)

Answer 1

n = p*(1-p) * (z-critical/error)**2

= 0.36 * 0.64 * (1.96/0.05)**2 = 354.04 ~ 355