Why isn’t every physicist a Bayesian?

Abstract

Physicists embarking on seemingly routine error analyses are finding themselves grappling with major conceptual issues which have divided the statistics community for years. While the philosophical aspects of the debate may be endless, a practicing experimenter must choose a way to report results. The results can depend on which of the two major frameworks, classical or Bayesian, one adopts. This article reviews reasons why most data analysis in particle physics has traditionally been carried out within the classical framework, and why this will probably continue to be the case. However, Bayesian reasoning has recently made significant inroads in some published work in this field, and many other particle physicists may frequently think in a Bayesian manner without realizing it. I illustrate the issues involved with a few simple, commonly encountered examples which reveal how each framework can sometimes lead to unsatisfying results.