🟢 Stats: What's a Conditional Probability?

P(A|B) means "probability of A, given B already happened."

P(A|B) = P(A and B) / P(B)

Example: Deck of cards. P(King | Face card)? - P(King AND Face card) = 4/52 (all Kings are face cards) - P(Face card) = 12/52 - P(King | Face card) = (4/52) / (12/52) = 4/12 = 1/3

This concept is the building block for Bayes' theorem, which we'll hit in Module 02.