Page 259 - Probability Demystified
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Appendix
Bayes’ Theorem
A somewhat more difficult topic in probability is called Bayes’ theorem.
Given two dependent events, A and B, the earlier formulas allowed you to
find P(A and B)or P(B|A). Related to these formulas is a principle developed
by an English Presbyterian minister, Thomas Bayes (1702–1761). It is called
Bayes’ theorem.
Knowing the outcome of a particular situation, Bayes’ theorem enables
you to find the probability that the outcome occurred as a result of a
particular previous event. For example, suppose you have two boxes
containing red balls and blue balls. Now if it is known that you selected a
blue ball, you can find the probability that it came from box 1 or box 2.
A simplified version of Bayes’ theorem is given next.
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