# What is the formula for Bayes' Theorem?

What is formula for Bayes' Theorem?

Bayes' Theorem is a way of finding a probability when we know other probabilities

In Bayes theorem, P(A) is probability of event A happening

P(B) is probability of event B happening

We can answer, How often event A happens given that event B happens, written P(A|B)

When we know how often event B happens given that event A happens, written P(B|A)

Let's say we are in San Francisco, Now P(Rain) for a given day in SFO is Probability of Rain = 10%

P(Cloud|Rain) is Probability of Cloud, given that Rain happens = 60%

P(Cloud) is Probability of Cloud in SFO = 20%

so probability that it will rain, given cloud is P(Rain|Cloud) can be calculated is shown in the video