You want to estimate the percentage of statistics students w

You want to estimate the percentage of statistics students who get grades of C or better. How many students should you survey to be 95% confident that the sample percentage is off by no more than 2 percentage points.

Solution

We use p=0.5 as estimated.

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

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

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

=2401