SOLUTION: A recent poll of 500 people showed that 325 of them exercise more than twice per week, if the researchers want to be 95% confident of their results to within 2.5%, how large a samp

Question 1022056: A recent poll of 500 people showed that 325 of them exercise more than twice per week, if the researchers want to be 95% confident of their results to within 2.5%, how large a sample is necessary?
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
z* sqrt{(p*(1-p)/n}=.025
z(.95)=1.96
sqrt{(p*(1-p)/n}=.025/1.96=0.128
don't round
square both sides and multiply by n
0.0001627n=0.65*0.35=0.2275; the 0.65 is the point estimate the sample gives, or 325/500.
0.2275=0.0001627 n
still without rounding, now divide both sides by 0.0001627
1398.24, and rounding up
1399 people

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