12 - other correlational techniques

Abstract

The Pearson correlation coefficient r is an appropriate statistic for describing the relationship between two variables when a linear model is appropriate and when data are continuous. For other kinds of data, however, other correlational techniques are necessary. The Spearman rank-order correlation coefficient, a Pearson r, is used when data are in the form of ranks. The point-biserial correlation coefficient, also a Pearson r, is used when one variable is dichotomous (has only two possible values) and one is continuous. This chapter describes the relationship between one dichotomous and one continuous variable. It examines the biserial correlation coefficient and tetrachoric correlation coefficient. When relationship between two variables is to be determined and both of them are genuinely dichotomous, the appropriate correlation coefficient to compute is the phi coefficient. This coefficient is closely related to the chi square statistic.