coefficient of correlation

n. A numerical index of shared relationship between two variables. The product-moment correlation is the most widely used correlation coefficient, measures linear relationship, and is appropriate for use with ratio variables and used with interval data. It shows relationship on a scale where 0 is no relationship, +1 is a perfect positive relationship, and -1 is a perfect negative relationship. Kendall’s tau is often used with ordinal variables, and Spearman’s rho is often used with rank order correlations.