SOLUTION: A recent poll of 700 people who work indoors found that 278 smoke. If the researchers want to be confident 98% of their results to within 3.5 percentage points, how large a sample

Question 1142495: A recent poll of 700 people who work indoors found that 278 smoke. If the researchers want to be confident 98% of their results to within 3.5 percentage points, how large a sample is necessary?
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
the half-interval needs to be 0.035
the half-interval is z*sqrt(p*(1-p)/n), p=278/700=0.397
this is 2.328* sqrt (0.397*0.603/n)<0.035
square both sides
5.420*0.239/n < 0.001225
1.295/0.001225 < n
n>1057.14 or 1058

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