Understanding Bayes’ Rule

Holt, Charles A., and Lisa R. Anderson. "Classroom Games: Understanding Bayes’ Rule." Journal of Economic Perspectives. 10 (Spring 1996) 179-187.

In this classroom situation, students learn to make Bayesian decisions. Materials needed include three marbles of one color, three of another color, a six-sided die and two identical plastic cups of a large size. Bath-oil beads may be substituted for the uniform marbles. Let urn A indicate a cup containing two red marbles and one white marble, and let urn B be a cup containing one red and two whites. A volunteer goes behind the class and rolls the die. A roll of 1, 2, or 3 results in a draw from urn A, while 4, 5, 6 earns draw from B, but the class should not see the actual die throw. Next, a single marble is drawn and shown to the class, and each student is asked to write down the probability that the draw came from urn A, along with their name and a short explanation of how they found the probability. A Figure provided in the article along with a list of questions will aid in this part of the experiment. The decision sheets are collected and tabulated. Discussion ensues and leads into Bayes’ Rule. More dimensions can be easily added, and interest can be added by rewards of quarters for correct answers, etc.