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How to Calculate the Expected Value of a Variable

To calculate the expected value of a variable requires basic calculus. The expected value is also called the mean (or average) of a random variable. It is actually the weighted average of all values that a random variable could assume. So to calculate the expected value, you must know the range of values that variable can take along with the probabilities of each potential value. The formula is the summation, taken across the range of possible values, of each value times its probability.

Instructions

- 1
  Calculate the sum of each weighted probability. To help out, start by making a table of all possible values for the variable with the probability of that value. If your range in infinite, make only enough entries in the table to write the nth value in terms of a formula. For these purposes, assume you have a finite number of possible values.
- 2
  Take the product of each value with its corresponding probability to create a weighted probability. If you like, make this value a third column of your table.
- 3
  Sum up the weighted probabilities and simplify the expression. The result is your expected value.

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