The estimate of the population proportion is to be within pl

The estimate of the population proportion is to be within plus or minus 0.04, with a 98% level of confidence. The best estimate of the population proportion is 0.25. How large a sample is required?

Solution

Compute Sample Size ( n ) = n=(Z/E)^2*p*(1-p)
Z a/2 at 0.02 is = 2.33
Samle Proportion = 0.25
ME = 0.04
n = ( 2.33 / 0.04 )^2 * 0.25*0.75
= 636.1992 ~ 637