Tell Me The Odds: A 15 Page Introduction To Bayes Theorem

Bayes’s much more famous work, “An Essay toward Solving a Problem in the Doctrine of Chances,”24 was not published until after his death, when it was brought to the Royal Society’s attention in 1763 by a friend of his named Richard Price. It concerned how we formulate probabilistic beliefs about the world when we encounter new data.

Bayes' Theorem looks at how likely something is to happen, given that something else has already happened.

If the philosophical underpinnings of Bayes’s theorem are surprisingly rich, its mathematics are stunningly simple. In its most basic form, it is just an algebraic expression with three known variables and one unknown one. But this simple formula can lead to vast predictive insights. Bayes’s theorem is concerned with conditional probability. That i

What Bayes’ theorem does is tell you how much you should change your belief. But in order to do that, you have to have a belief in the first place.

Bayes’s theorem begins and ends with a probabilistic expression of the likelihood of a real-world event. It does not require you to believe that the world is intrinsically uncertain. It was invented in the days when the regularity of Newton’s laws formed the dominant paradigm in science. It does require you to accept, however, that your subjective

he discovered the long-sought grail of probability, what future mathematicians would call the probability of causes, the principle of inverse probability, Bayesian statistics, or simply Bayes’ rule.