An **event** is any subset $E \subseteq S$ of the sample space. $E$ is a collection of outcomes. --- > [!example]- Event of an even number. > For a six-sided die, the sample space is $S = \{1,2,3,4,5,6\}$. The event $E = \{2, 4, 6\}$ contains 3 of the 6 equally likely outcomes. > $ P(E) = \frac{|E|}{|S|} = \frac{3}{6} = 0.5 $