Question 1157326: A political candidate has asked you to conduct a poll to determine what percentage of people support her.
If the candidate only wants a 8% margin of error at a 95% confidence level, what size of sample is needed?
Give your answer in whole people.
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! 8% error means z*SE=0.08; z(0.975)=1.96
SE=sqrt(.5*.5/n), because the probability of people supporting is not known. When that happens, use 0.5 as it gives the most conservative estimate. The largest product of two fractions that add to 1 occurs when both are 1/2.
so 1.96* sqrt(.25/n)=0.08
square both sides
3.84*.25=0.0064*n, moving the n across
n=150 people
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