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Answers for “如何利用观测值更新概率?”

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Understand why

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The probability of A given B and the probability of B given A are generally different because they condition on different events. Bayes' theorem connects these two conditional probabilities by incorporating the prior probabilities of the individual events, P(A)P(A) and P(B)P(B).

Conditions: A and B are events in a probability space.; P(B)>0P(B) > 0 and P(A)>0P(A) > 0.

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Bayes' formula is derived by expressing the joint probability of the intersection of events A and B, P(A∩B)P(A \cap B), in two different ways using the definition of conditional probability. By equating these two expressions, P(A∣B)P(B)P(A|B)P(B) and P(B∣A)P(A)P(B|A)P(A), and then dividing by P(B)P(B), we isolate P(A∣B)P(A|B) to obtain Bayes' theorem.

Conditions: P(B)>0P(B) > 0 to allow division.; Events A and B are defined in the same probability space.