How large a sample size would be needed to estimate the perc

How large a sample size would be needed to estimate the percentage of wireless routers in San Francisco that use data encryption, with an error of

Solution

Given a=1-0.95=0.05, Z(0.025) = 1.96 (from standard normal table)

We use p=0.5 as estimated.

So n=(Z/E)^2*p*(1-p)

=(1.96/0.02)^2*0.5*0.5

=2401