Expected value

Average value of a random variable

In probability theory, the expected value (also called expectation, mean, or first moment) is a generalization of the weighted average. Provided that it is finite, the expected value can be interpreted as the long-run average of results from independent repetitions of the same random experiment, as formalized by the law of large numbers. For a random variable that takes finitely many values, the expected value is the weighted average of those values, with their probabilities as weights.

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