principles.fyi · the brain · concept

probability

A number from 0 to 1 telling how likely something is.

P(everything) = p1 + p2 + p3 + ... = 1

Probability is a number that measures how likely something is, on a scale from 0 (it never happens) to 1 (it always happens). Think of one whole pie cut into slices, one slice per possible outcome, where a bigger slice means "more likely." Because exactly one outcome must happen, all the slices together make a full pie, so the probabilities always add up to 1. A transformer predicts the next word this way: it hands every possible word a slice, and the biggest slice is its best guess.