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Prior probability

prior probability
The best rational assessment of the probability of an outcome on the basis of established knowledge before the present information is included. For instance, the prior probability of the daughter of a carrier of haemophilia being herself haemophiliac is 1/2. But if she already has one child, an affected son, the posterior probability that she is a carrier is unity, whereas if she has one child, a normal one, the posterior probability that she is a carrier is 1/3.
See: bayes theorem.


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