Frequencies

Abstract

Particularly in the social sciences, the most common form of statistical data is a frequency, i.e. the number of propositions of a certain kind which are observed to be true. Examples are the number of houses in a street which are inhabited by six or more people, or the number of people in a sample who say they will vote for a particular political party. In our study of trials and deals we considered two special structures for frequencies. This chapter introduces a much more general structure, called exchangeability. Exchangeable sequences of propositions are defined in Section 8.1. Sections 8.2^- and 8.3 present a measurement device, by extending the argument, for probabilities in exchangeable sequences. Section 8.2 deals with finite sequences, whereas the more important case of infinite exchangeable sequences is dealt with in Section 8.3.