Difference between revisions of "Some Probability Formulas"
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Revision as of 12:33, 11 February 2022
Some useful probability formulas
The Addition Rule
Consider 2 events, A and B. To find the probability that either A or B (or both) will occur, we can use the following formula, called the addition rule:
We subtract the probability of both A and B occurring, as to not "double count" them. This can seen better by looking at the following Venn Diagram:
Conditional Probability
Sometimes we would like to know the probability of an event B occurring, given that another event A has already occurred. This in called conditional probability and we use the notation:
This is read as "The probability of B given A," and can be calculated as follows:
Contributed by David Ciskowski
