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Learn how to estimate the percentage of a group with a particular property by having members flip coins and analyze the results. Understand the process of calculating probabilities and preparing for awkward questions. Use independence to estimate accurately.
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Estimating the answer to an embarrassing question To estimate what percentage of a group has property P, ask each member of the group to flip a coin and raise a hand if the flip is heads (H) or the individual has P Assumptions: H and P are independent ¬P is not embarrassing Everyone answers honestly
Calculating Pr(P) from Pr(H∪P) H P Because H and P are independent events, Pr(H∩P) = Pr(H) ∙ Pr(P). Pr(H) = .5 Pr(H∪P) = Pr(H) + Pr(P) - Pr(H∩P). So Pr(P) = Pr(H∪P) - Pr(H) + Pr(H)∙Pr(P) Pr(P) = 2 ∙ Pr(H∪P) – 1