SOLUTION: Veronica has observed 200 bicycles at an intersection and found that 80% did not make a complete stop. Veronica tells you that the margin of error was 4%. What was the confidence l

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Question 564989: Veronica has observed 200 bicycles at an intersection and found that 80% did not make a complete stop. Veronica tells you that the margin of error was 4%. What was the confidence level of the study?
Answer by stanbon(75887) About Me  (Show Source):
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Veronica has observed 200 bicycles at an intersection and found that 80% did not make a complete stop. Veronica tells you that the margin of error was 4%. What was the confidence level of the study?
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ME = z*sqrt(pq/n)
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0.04 = z*sqrt[0.8*0.2/200)
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0.04 = z*0.0283
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z = 1.4142
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normalcdf(1.4142,100) = 0.0786
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Confidence level = 1 - 2*0.0786 = 84.27%
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Cheers,
Stan H.
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