When I ask, how many of you believed in Santa Claus or the tooth fairy for the larger part of your lives, I already know it will be all of you because as kids your malleable brains were still developing to assess the evidence. Here is when Reverend Thomas Bayes comes in with his ‘Bayes’ Theorem’. Bayes Theorem While his theorem remained unpublished during his lifetime, it became greatly beneficial in many areas. Bayes' theorem states that the probability of A given B is the same as the probability of B given A times the probability of A, divided by the probability of B. It sounds a bit mouthful but it allows us to determine the chance of certain events happening when we know the probabilities of other related events beforehand. Ever wondered how the weather is forecasted? By using the Bayes theorem. To understand the formula better, let us get our hands dirty by doing some math. What is the first sign you would look for it to rain? The clouds. So, to find the probability of ...