Applied statistics/Tutorials
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Rules of chance
The addition rule
For two mutually exclusive events, A and B,
the probability that either A or B will occur is equal to the probability that A will occur plus the probability that B will occur,
- P(A or B) = P(A) + P(B).
The multiplication rule
For two independent (unrelated) events, A and B,
the probability that A and B will both occur is equal to the probability that A will occur multiplied by the probability that B will occur,
- P(A and B) = P(A) x P(B)
Bayes' theorem
The probability that event A will occur, given that event B has occurred is equal to the probability that B will occur, given that A has occurred, mutiplied by the probability that A will occur divided by the probability that B will occur,
- P(A/B) = P(B/A) x P(A)/P(B).