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Published byEvelyn Reynolds Modified over 9 years ago
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The sample space (omega) collectively exhaustive for the experiment mutually exclusive right scope ‘granularity’ The probability law assigns a probability to every event in the sample space satisfies the axioms of probability
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Nonnegativity: P(A)>=0 for all A Additivity: If A and B are disjoint sets, then the probability of their union is the sum of the probabilities of the set. Normalization: P(omega)=1 All other equations relating to probability laws are ultimately derived from the above axioms.
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A shift into a new, related sample space, with a new probability law The new law still satisfies the axioms of probability The definition on page 20 could be written in words, “Whatever even A occurs must occur within the event B, so B is now the entire sample space.” relative probabilities are maintained Alternatively, the conditional probability could be viewed as remaining on the same sample space omega, but normalized by B.
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Partition the sample space into A1…An then P(B) is the probability of B found in each set Ai summed over all i This amounts to P(B) being a weighted average of P(B|Ai) summed over all i, with P(Ai) as the weighting factor
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The probability of a series of events is the product of the probability of each event in the series, conditioned on the previous event
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A way to infer the probability of an event Ai as a cause, out of i possible causes for event B, which has been observed. We want to know the probability of Ai|B B has been observed, so the probability of the B also falling within the event Ai should be the ratio of the the probability of B occurring and being in event Ai (i.e. P(A)*P(B|Ai)) to the probability of B occurring at all. Verifiable by the definition of conditional probability (see pg. 20 and pg 32).
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