# Bayes rule

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Related to Bayes rule: conditional probability

## Bayes rule

[′bāz ‚rül] (statistics)

The rule that the probability

*P*(*E*|_{i}*A*) of some event*E*, given that another event_{i}*A*has been observed, is*P*(*E*)_{i}*P*(*A*|*E*)/_{i}*P*(*A*), where*P*(*E*) is the prior probability of_{i}*E*, determined either objectively or subjectively, and_{i}*P*(*A*), the probability of*A*, is given by the sum over all possible events*E*of the quantity_{j}*P*(*E*)_{j}*P*(*A*|*E*)._{j}Want to thank TFD for its existence? Tell a friend about us, add a link to this page, or visit the webmaster's page for free fun content.

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