Expected Value

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Calculate

Example: a shop sells 0, 1, 2 or 3 units of a product a day, with chances of 10%, 30%, 40% and 20%. How many units does it sell per day, on average? Change the values to work out your own case.

Possible values x_i Separated by spaces or commas. Probabilities P(x_i) In the same order as the values, adding up to 1 or 100 (in %).

Step by step

What each term means

Expected Value (E[X]): The long-run average of the random variable X: the value the mean of the outcomes settles around when the experiment is repeated many times. Also written μ.
Summation (Σ): Adds over every possible value of X. The probabilities of all of them must add up to 1.
Possible Value (xᵢ): Each outcome X can take, such as the number of sales in a day or the prize in a game.
Probability (P(xᵢ)): The chance that X equals exactly xᵢ. It works as a weight: more likely values pull the expected value towards themselves.