#math #stats
the probability of both events happening
$$P(A\cap B) = P(A)P(B|A)$$
since if B were to be dependent upon A, we don't want to essentialy count the probability of A happening twice, so we have to seperate it with $P(B|A)$
if both A and B are **independent**,
$$P(A\cap B) = P(A)P(B)$$