Conditional Probability & Bayes

1 / 3

Memorize

The 82%-frequency formula. P(A given B) = probability of A knowing that B happened.

P (A ∣ B) = \frac{P ( A \cap B )}{P ( B )}

'A given B' = joint probability over the condition

$P (A \cap B)$

Joint probability

Both A and B happen

$P (B)$

The condition

We're told B happened — restrict universe

Ratio

Conditional probability

How much of B's probability is also A