In this clearly and graphically explained educational video, Amber Biology offers an intuitive introduction to Bayes’ Theorem, using biomarkers and ovarian cancer testing as an example for life science applications of the Bayesian approach. As the authors state, “Bayes’ Theorem is something that every scientist, physician and engineer should understand, but it also has far wider applications in all aspects of our lives in which decisions must be made based upon the weighing of evidence.”