Partition

If we have events that are completely disjoint, we define them as follows:

Partition

Events $A_{1}, . . ., A_{k}$ form a partition of a sample space $S$ if exactly one of these events must occur when the experiment is performed - that is if $A_{1} \cup \dots \cup A_{k} = S$ and $A_{i} \cap A_{j} = \emptyset$ for $i \neq j$ . The events are exhaustive and mutually exclusive.