Bayes factors with an application to experimental economics

We describe Bayes factor, an explicit measure of the strength of the evidence, the extent to which the data increase or decrease the odds a given hypothesis or model is true. Issues and techniques for deriving a Bayes factor are outlined. We illustrate the technique with data from an ultimatum game experiment that looked for an experimenter observation effect. We show that the evidence increases the odds of an effect, but not by enough to convince someone with a skeptical prior.