<Table> <Tr> <Td> </Td> <Td> This article includes a list of references, but its sources remain unclear because it has insufficient inline citations . Please help to improve this article by introducing more precise citations . (October 2009) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article includes a list of references, but its sources remain unclear because it has insufficient inline citations . Please help to improve this article by introducing more precise citations . (October 2009) (Learn how and when to remove this template message) </Td> </Tr> <P> In logic and probability theory, two events (or propositions) are mutually exclusive or disjoint if they cannot both occur at the same time (be true). A clear example is the set of outcomes of a single coin toss, which can result in either heads or tails, but not both . </P> <P> In the coin - tossing example, both outcomes are, in theory, collectively exhaustive, which means that at least one of the outcomes must happen, so these two possibilities together exhaust all the possibilities . However, not all mutually exclusive events are collectively exhaustive . For example, the outcomes 1 and 4 of a single roll of a six - sided die are mutually exclusive (both cannot happen at the same time) but not collectively exhaustive (there are other possible outcomes; 2, 3, 5, 6). </P>

What does it mean when two events are mutually exclusive