Comment on What are the most mindblowing fact in mathematics?

• eran_morad@lemmy.world ⁨1⁩ ⁨year⁩ ago

  read up on the law of total probability. prob(car is behind door #1) = 1/3. monty opens door #3, shows you a goat. prob(car behind door #1) = 1/3, unchanged from before. prob(car is behind door #2) + prob(car behind door #1) = 1. therefore, prob(car is behind door #2) = 2/3.

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  • Kissaki@feddit.de ⁨1⁩ ⁨year⁩ ago

    Following that cascade, didn’t you just change the probability of door 2? It was 1/3 like the other two. Then you opened door three. Why would door two be 2/3 now? Door 2 changes for no disclosed reason, but door 1 doesn’t?

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    • eran_morad@lemmy.world ⁨1⁩ ⁨year⁩ ago

      No, you didn’t change the prob of #2. Prob(car behind 2) + prob(car behind 3) = 2/3. Monty shows you that prob(car behind 3) = 0.

      This can also be understood through conditional probabilities, if that’s easier for you.

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