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COnDITIONAL Probability. Onur DOĞAN. The Definition of Conditional Probability.
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COnDITIONALProbability Onur DOĞAN
The Definition of Conditional Probability A major use of probability in statistical inference is the updating of probabilitieswhen certain events are observed. The updated probability of event A after welearn that event B has occurred is the conditional probability of A given B.
IndependentEvents If learning that B has occurred does not change the probability of A, then we saythat A and B are independent. There are many cases in which events A and Bare not independent, but they would be independent if we learned that some otherevent C had occurred. In this case, A and B are conditionally independent given C.
Bayes’ Theorem Suppose that we are interested in which of several disjoint events B1, . . . , Bk willoccur and that we will get to observe some other event A. If Pr(A|Bi) is availablefor each i, then Bayes’ theorem is a useful formula for computing the conditionalprobabilities of the Bi events given A.