Bayesian Theory Evaluator

This is an important-sounding name for a very modest program designed to illustrate the application of Bayes's Theorem to issues in the philosophy of science. You supply the prior probability P(T) of a theory or hypothesis T; the likelihood P(E|T), i.e. the probability that a new piece of evidence E is true given that T is true; and and the probability P(E|~T) that E is true given that T is false. Then click on the P(T|E) button to have the computer calculate the posterior probability P(T|E), i.e. the probability that the theory is true given that the evidence is true.

This is a Java applet that makes use of the Swing classes. It probably won't work correctly in Microsoft Internet Explorer unless you install Sun's Java Plugin, which is free and easy to install.

The calculation follows this version of Bayes's Theorem:

Last update: February 18, 2002
Curtis Brown | Philosophy of Science | Philosophy Department | Trinity University