Bayes’ Theorem: Bayes’ theorem, named after 18th-century British mathematician Thomas Bayes, helps to determine the conditional probability of an event. Conditional probability is the probability of an event happening, given that occurrence of the event is affected by one or more other events.
Bayes’ theorem provides a way to update the existing probability of occurrence on an event based on availability of new or additional events.
Or we can describe Bayes’ theorem as
P(A|B): is a conditional probability: the likelihood of event A occurring given B has already occurred
P(B|A): is a conditional probability: the likelihood of event B occurring given A has already occurred
P(A) or P(B): Unconditional probability of occurrence event A and B independent of each other also known as marginal probability
Incase Event A and B are independent and one event do affect the occurrence of other event then