To me, the single most easy to understand form of Bayes' Theorem is: P(A|B) * P(B) = P(A∩B) = P(B|A) * P(A) An intuitive explanation to the equation: The

To me, the single most easy to understand form of Bayes' Theorem is: P(A|B) * P(B) = P(A∩B) = P(B|A) * P(A) An intuitive explanation to the equation: The (possibility of events A and B both happening) equals the (possibility of A happening when B is happening) * the (possibility of B happening), which equals to the (possibility of B happening when A is happening) * the (possibility of A happening). Combining that with a Venn diagram: {A (A}∩{B) B} Since P(B|A) means the chance of event B happening when A is happening, in this case which indicates that both A and B are happening, it's really just the area of (A∩B) divided by (A), which can be translated to (P(A|B) * P(B)) / P(A).