CHAPTER 2 - Measures of Relationship between Two Variables

Abstract

This chapter discusses the measures of relationship between two variables. The chapter presents the double-entry table, or scatter diagram, that has been used to picture the relationship between any two variables. Interest in individual differences and their genetic inheritance led to seek ways of measuring the degree of relationship. The chapter presents the case of Pearson r, assuming that both X and Y are interval or ratio scores. Much data collected by psychologists are not of that type, and the researcher may find that one or both of the variables consists of ranks (ordinal scales), dichotomies (two classes), or multichotomies (three classes or more). For some combinations of such variables, special equations have been developed by substituting equivalent values into the raw score equation for Pearson r. On the computer, any one or any combination of such variables can be processed to obtain a correlation or an inter,-correlation matrix by the regular Pearson r program. It explains that for the measures based upon ranks, the computer output using the Pearson equation will already be corrected for the cases when pseudovariates are tied.