P(A|B) is the probability of A happening when B happens;

P(A) is the probability of A happening;

P (B|A) is the probability of B occurring if A occurs;

P(B) is the probability of B occurring.

P(B) = P(B丨A)P(A)+P(B丨A')P(A')... This is called the total probability formula.

P(A'), the probability that A does not occur, P(A') = 1- P(A).

Bayes' theorem is a method of solving probabilities given other probabilities are known. Bayes' theorem, as a commonly used basic algorithm, has always been of great significance and application in statistics, psychology, sociology, economics, etc. Entering the IT era, Bayes' theorem occupies an important place in computer science, especially in machine learning and artificial intelligence. Especially in terms of data processing, it has good results in analyzing the probability of event occurrence and the credibility of events. In recent years, Bayes' theorem has received more and more attention and application in the analysis and market prediction of securities, futures, etc.

Bayes (1701-1761) Thomas Bayes, British mathematician. Born in London in 1701, he worked as a priest. In 1742, he became a member of the Royal Society. Died on April 7, 1761. In mathematics, Bayes mainly studies probability theory. He first applied inductive reasoning to the basic theory of probability theory, and founded Bayesian statistical theory, making contributions to statistical decision functions, statistical inference, and statistical estimation.