In this chapter we discuss Bayesian hypothesis testing. We begin with some historical background regarding how hypothesis testing has been treated in science in the past, and show how the Bayesian approach to the subject has really provided the statistical basis for its development. We then discuss some of the problems that have plagued fiequentist methods of hypothesis testing during the twentieth century. We will treat two Bayesian approaches to the subject:1. The vague prior approach of Lindley (which is somewhat limited but easy to implement); and 2. The very general approach of Jefkys, which is the current, commonly accepted Bayesian niethod of hypothesis testing, although it is somewhat more complicated to carry out.
A BRIEF HISTORY OF SCIENTIFIC HYPOTHESIS TESTINGThere is considerable evidence of ad hoc tests of hypotheses that were developed to serve particular applications (especially in astronomy), as science has developed. But there had been no underlying theory that could serve as the basis for generating appropriate tests in general until Bayes' theorem was expounded. Moreover, researchers had difficulty applying the theorem even when they wanted to use it. Karl Pearson (1 892), initiated the development of a formal theory of hypothesis testing with his development of chi-squared testing for multinomial proportions. Me liked the idea of applying Bayes' theorem to test hypotheses, but he could not quite figure out how to generate prior distributions to support the Bayesian approach. Moreover, he did not recognize that corwideration of one or more! alternative hypotheses might be relevant for testing a basic scientific hypothesis.