# Chapter 3 Interpretations of Probability and Statistics

You have some familiarity with “probability” or “chance” or “odds”. But what do we really mean when talk about “probability”? It turns out there are two main interpretations: relative frequency and “subjective” probability. These two interpretations provide the philosophical foundation for two schools of statistics: frequentist (hypothesis tests and confidence intervals that you’ve seen before) and Bayesian (what this book is about). This chapter introduces the two interpretations.