Craps principle
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In probability theory, the craps principle is a theorem about event probabilities under repeated iid trials. Let and
denote two mutually exclusive events which might occur on a given trial. Then the probability that
occurs before
equals the conditional probability that
occurs given that
or
occur on the next trial, which is
The events and
need not be collectively exhaustive (if they are, the result is trivial).[1][2]