SOLUTION: You want to obtain a sample to estimate a population proportion. At this point in time, you have no reasonable estimate for the population proportion. You would like to be 99.9% co

Question 1103901: You want to obtain a sample to estimate a population proportion. At this point in time, you have no reasonable estimate for the population proportion. You would like to be 99.9% confident that you estimate is within 5% of the true population proportion. How large of a sample size is required?

Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
Want a half-interval of 0.05
half-interval is z*sqrt(p*(1-p)/n), where p=0.5 to maximize the value of the sample size (most conservative).
z*0.5/sqrt(n)=0.05
square both sides and multiply both sides by n.
z^2*0.25=0.0025n
z=3.3
10.89*0.25=0.0025 n
n=1089

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