Invited talk at the XVIII International Workshop on Maximum Entropy and Bayesian Methods (Maxent98), Garching / München (Germany), July 27-31 1998. physics/9811046

Abstract. The intuitive reasoning of physicists in conditions of uncertainty is closer to the Bayesian approach than to the frequentist ideas taught at University and which are considered the reference framework for handling statistical problems. The combination of intuition and conventional statistics allows practitioners to get results which are very close, both in meaning and in numerical value, to those obtainable by Bayesian methods, at least in simple routine applications. There are, however, cases in which ``arbitrary'' probability inversions produce unacceptable or misleading results and in these cases the conscious application of Bayesian reasoning becomes crucial. Starting from these considerations, I will finally comment on the often debated question: ``is there any chance that all physicists will become Bayesian?''

Key words: Subjective Bayesian Theory, High Energy Physics, Measurement Uncertainty

Table of Contents

INTRODUCTION

MEASUREMENT UNCERTAINTY

PROFESSED FREQUENTISM VERSUS PRACTICED SUBJECTIVISM

HEP physicists ``are frequentist''

HEP physicists ``are Bayesian''

Intuitive application of Bayes' theorem

Bayes versus Monte Carlo

EXPLICIT USE OF BAYESIAN METHODS IN HEP

EXAMPLES OF MISLEADING RESULTS INDUCED BY CONVENTIONAL STATISTICS

Claims of new physics based on p-values

What does a lower mass bound mean?

CONCLUSIONS

REFERENCES

For a postscript version of the article, click here.