Bayes' Rule

Given two events $A$ and $B$ and their probabilities, the conditional probability $P(A|B)$ can be expressed in terms of the reverse conditional probability $P(B|A)$ as follows:

$P\left(A\mid B\right)={\frac {P\left(B\mid A\right)\,P\left(A\right)}{P\left(B\right)}}$