^{ Type post Author Jonathan Bartlett Date November 30, 2020 Categorized Artificial Intelligence, Mathematics Tagged __featured, Bayes’ Rule, Bayesian reasoning, False positives, HIV, Probability, Risk, Screening tests, Thomas Bayes }

## Can an 18th Century Statistician Help Us Think More Clearly?

_{Distinguishing between types of probability can help us worry less and do more}

_{ Jonathan Bartlett November 30, 2020 Artificial Intelligence, Mathematics }

Thomas Bayes (1702–1761) (pictured), a statistician and clergyman, developed a theory of decision-making which was only discussed after his death and only became important in the 20th century. It is now a significant topic in philosophy, in the form of Bayesian epistemology. Understanding Bayes’ Rule may be essential to making good decisions. Let’s say that you are a generally healthy person and have no symptoms of any illness and no specific risk factors for any illness. Acting on a friend’s suggestion, you get screened for a variety of diseases, just to be sure. Of the diseases you test for, the HIV test comes back positive. You read on the package that the test is 99.6% accurate. Are you more likely…