## ::Event (probability theory)

### ::concepts

Space::sample Event::events Elements::subset Theory::subsets Example::books Numbers::-algebra

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In probability theory, an **event** is a set of outcomes of an experiment (a subset of the sample space) to which a probability is assigned.<ref>{{#invoke:citation/CS1|citation
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}}</ref> An event defines a complementary event, namely the complementary set (the event *not* occurring), and together these define a Bernoulli trial: did the event occur or not?

Typically, when the sample space is finite, any subset of the sample space is an event (*i*.*e*. all elements of the power set of the sample space are defined as events). However, this approach does not work well in cases where the sample space is uncountably infinite, most notably when the outcome is a real number. So, when defining a probability space it is possible, and often necessary, to exclude certain subsets of the sample space from being events (see *Events in probability spaces*, below).

**Event (probability theory) sections**

Intro A simple example A note on notation See also Notes External links

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