# Basic Statistics & Probability

### Topics

**Complementary events** are two outcomes of an event that are the *only two possible outcomes*.

- This is like flipping a coin and getting heads or tails. Of course, there are no other options, so these events are complementary.
- Rolling a die and getting a 1 or 2 are
*not*complementary, since there are other outcomes that may happen (3, 4, 5, or 6). - However, rolling a die and getting a 1 or not-a-1 are complementary (you have to roll either a 1 or not-a-1).

**Mutually exclusive events** are two or more outcomes of an event that *cannot occur at the same time*.

- Picking one card from a standard deck and choosing an ace or a king are mutually exclusive events (since you can't do both at the same time).
- However, choosing a red card or a king are not mutually exclusive (you could choose a red king).

*All complementary events are mutually exclusive, but all mutually exclusive events are not necessarily complementary.*

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