- The probability of an event describes the likelihood an event will occur. The likelihood of an event ranges from impossible to certain, but more common descriptions are likely to unlikely. An event is a single outcome or a group of outcomes. An outcome is a possible result of an action. Probability can be represented as a fraction, as a decimal, or as a percent. Something is fair if there is an equal chance for each outcome to occur.
1 out of 10, or
. It is unlikely to occur.