page_title: Outcome (probability)
section_title: Equally likely outcomes
hierarchical_section_title: Outcome (probability) / Equally likely outcomes
caption_attribution_description: English: Tossed coin.
context_page_description: In probability theory, an outcome is a possible result of an experiment or trial. Each possible outcome of a particular experiment is unique, and different outcomes are mutually exclusive. All of the possible outcomes of an experiment form the elements of a sample space.
  For the experiment where we flip a coin twice, the four possible outcomes that make up our sample space are, and, where "H" represents a "heads", and "T" represents a "tails". Outcomes should not be confused with events, which are sets of outcomes. For comparison, we could define an event to occur when "at least one 'heads'" is flipped in the experiment - that is, when the outcome contains at least one 'heads'. This event would contain all outcomes in the sample space except the element.
context_section_description: In some sample spaces, it is reasonable to estimate or assume that all outcomes in the space are equally likely (that they occur with equal probability). For example, when tossing an ordinary coin, one typically assumes that the outcomes "head" and "tail" are equally likely to occur. An implicit assumption that all outcomes are equally likely underpins most randomization tools used in common games of chance (e.g. rolling dice, shuffling cards, spinning tops or wheels, drawing lots, etc.). Of course, players in such games can try to cheat by subtly introducing systematic deviations from equal likelihood (e.g. with marked cards, loaded or shaved dice, and other methods).
  Some treatments of probability assume that the various outcomes of an experiment are always defined so as to be equally likely. However, there are experiments that are not easily described by a set of equally likely outcomes— for example, if one were to toss a thumb tack many times and observe whether it landed with its point upward or downward, there is no symmetry to suggest that the two outcomes should be equally likely.
caption: Flipping a coin leads to two outcomes that are almost equally likely.
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