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Three-person jury with a coin-flipping member

Question

Panel A has three members deciding by majority vote: two of them are each independently right with probability pp, while the third decides every case by tossing a fair coin. Panel B is one person who is right with probability pp. Which panel is more likely to reach the correct verdict?

Short answer

Neither — both are correct with probability pp. Panel A is right when the two serious members both are right (p2p^2), or when they split (2p(1−p)2p(1-p)) and the coin sides with the right one (half the time). That totals p2+p(1−p)=pp^2+p(1-p)=p.

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