# Difference between revisions of "Expected value"

From Lesswrongwiki

Steven0461 (talk | contribs) |
m (added links to Arbital) |
||

(One intermediate revision by one other user not shown) | |||

Line 1: | Line 1: | ||

{{wikilink}} | {{wikilink}} | ||

− | + | {{Arbitallink|https://arbital.com/p/expected_value/|Expected value}} | |

The '''expected value''' or '''expectation''' is the (weighted) average of all the possible outcomes of an event, weighed by their [[probability]]. For example, when you roll a die, the expected value is (1+2+3+4+5+6)/6 = 3.5. | The '''expected value''' or '''expectation''' is the (weighted) average of all the possible outcomes of an event, weighed by their [[probability]]. For example, when you roll a die, the expected value is (1+2+3+4+5+6)/6 = 3.5. | ||

## Latest revision as of 02:23, 14 October 2016

The **expected value** or **expectation** is the (weighted) average of all the possible outcomes of an event, weighed by their probability. For example, when you roll a die, the expected value is (1+2+3+4+5+6)/6 = 3.5.

(Since a die doesn't even have a face that says 3.5, this illustrates that very often, the "expected value" isn't a value you actually expect.)