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Fuzzy Math: Impartial Jury

A bad jury or judge? Might as well flip a coin.

By Alex Stone
Apr 2, 2007 5:00 AMNov 12, 2019 6:05 AM


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Let’s say you’ve been put on trial—you’re innocent, of course—and that a perverse exercise in probability theory will decide your fate.

Each juror will choose whether or not to vote in favor of your conviction by flipping a coin: If it lands on heads, then it’s off with yours; if the coin lands on tails, then you are spared. But you have a choice. You can either select a three-person jury composed entirely of coin flippers—best out of three determines the verdict—or you can have the judge flip a single coin for the decision. Which scenario should your legal counsel request?

The truth is that it’s a trick question, since comparing the probabilities reveals that your odds of winning are a straight fifty-fifty shot in either case! You may as well let the judge decide and save three people from jury duty.

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