Glossary · Phase 2 · Math, when you need it
Probability
How likely something is, from 0 (never) to 1 (certain).
The probability of an event is a number from 0 to 1 that says how likely it is. 0 means it never happens. 1 means it always happens. 0.5 is a coin toss. You can also say it as a percentage: 0.25 is 25%.
Try it now
Work out "none" first, then take it away from 1. Note that it's far less than just adding the chances.
Learn it properly
Probability basics · Events, outcomes and the rules for combining them. About 25 minutes.
Other terms from the same lesson
- complement: Everything except the event: the chance something does not happen is 1 minus the chance it does.
- independent: Two events are independent when one happening doesn't change the chance of the other, like two separate coin flips.
- mutually exclusive: Events that can't both happen at once, like a die showing 2 and showing 5. Their chances simply add.
- seed: A starting number for a random generator. The same seed gives the same "random" numbers every run, so results can be repeated.
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