ABSTRACT
This chapter presents the common statistics that are used to summarize the relationship between two variables. It presents the statistics that are most commonly used to answer the questions, and explains that when it is appropriate to use them. It then discusses the most common measures of association and significance for each of the levels of measurement. The test of statistical significance for nominal variables is chi-square. A widely used coefficient of association for ordinal variables is G, or gamma, which works according to the same principle of error reduction as, but focuses on predicting the ranking or relative position of cases rather than simply their membership in a particular class or category. The chapter considers the likelihood that any association observed among cases sampled from a larger population is in fact a characteristic of that population and not merely an artifact of the smaller and potentially unrepresentative sample.
