Statistics Dictionary

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Expected Value

The mean of the discrete random variable X is also called the expected value of X. Notationally, the expected value of X is denoted by E(X). Use the following formula to compute the mean of a discrete random variable.

E(X) = Σ [ xi * P(xi) ]

where xi is the value of the random variable for outcome i, and P(xi) is the probability that the random variable will be equal to outcome i.

See also:   Attributes of Random Variables