The Concept of Probability in Psychological Experiments

Probability theory is seen as a branch of mathematics, representing no more than an application of measure theory, and classification of probability interpretations is discussed.

Abstract

This chapter discusses concept of probability in psychological experiments. Probability theory, in the chapter, is seen as a branch of mathematics, representing no more than an application of measure theory. The chapter discusses classification of probability interpretations. The attributes objective and subjective are used. Subjective probabilities are here seen as degrees of belief and may also be called “personal probabilities.” One can distinguish between the concept of subjective probability intended to describe actual behavior, which is typically what interests psychologists, and subjective probability theory aimed at characterizing coherent behavior. Coherence is equivalent to the condition that the laws of probability be obeyed. Objective interpretations can be based on arguments of symmetry, that is, equiprobable cases, or arguments that “objective probability is revealed by frequency.” An objective probability is then seen as a physical property of an object that can be estimated with sufficient precision by repeated measurement under identical conditions.