A quick introduction to expected value formulas. Expected Value Formula. Stephanie Glen. Loading. The formula for the expected value is relatively easy to compute and involves several multiplications and additions. This article is about the term used in probability theory and statistics. For other uses, see Expected value (disambiguation). In probability theory, the expected value of a random variable, intuitively, is the long-run .. This is because an expected value calculation must not depend on the order in which the possible outcomes. For example, EV applies well to gambling situations to describe expected results for thousands of gamblers per day, repeated day after day after day. Help answer questions Start your very own article today. More practically, the expected value of a discrete random variable is the probability-weighted average of all possible values. Two thousand tickets are sold. Neither gain nor lose 4. The expected value formula changes a little if you have a series of trials for example, a series of coin tosses. Already answered Not a question Bad question Other. Knowing such information can influence you decision on whether to play. Dies ist äquivalent mit. Updated May 07, Probability is the chance that each particular value or outcome may occur. More practically, the expected value of a discrete random variable is the probability-weighted average of all possible values. Expected values can also be used to compute the variance , by means of the computational formula for the variance. Definition and Calculating it was last modified: Es wird eine Münze geworfen. The convergence is relatively slow: All text shared under a Creative Commons License. Conceptually, the variance of a discrete random variable is the sum of the difference between each value and the mean times the probility of obtaining that value, as seen in the conceptual formulas below:. This gambling game has asymmetric values assigned to the various rolls, according to the rules of the game. The idea of the expected value originated in the middle of the 17th century from the study of the so-called problem of points , which seeks to divide the stakes in a fair way between two players who have to end their game before it's properly finished. Knowing the expected value is not the only important characteristic one may want to know about a set of discrete numbers: See the figure for an illustration of the averages of longer sequences of rolls of the die and how they converge to the expected value of 3. Add up the values from Step 1: This is because, when the first i tosses yield tails, the number of tosses is at least i.