| rank-difference correlation | The relationship between paired series of measurements, each ranked according to magnitude, which yields a coefficient known as rho; the value of rho varies from zero (no relationship) to +1.00 (perfect relationship). (05 Mar 2000) |
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| correlation | <statistics> most generally, the degree to which one phenomenon or random variable is associated with or can be predicted from another. In statistics, correlation usually refers to the degree to which a linear predictive relationship exists between random variables, as measured by a correlation coefficient. Correlation may be positive, i.e., both variables increase or decrease together or negative or inverse, i.e., one variable increases when the other decreases. (18 Nov 1997) |
| correlation coefficient | A measure of association that indicates the degree to which two variables have a linear relationship; this coefficient, represented by the letter r, can vary between +1 and -1; when r = +1, there is a perfect positive linear relationship in which one variable relates directly with the other; when r = -1, there is a perfect negative linear relationship between the variables. (05 Mar 2000) |
| product-moment correlation | A statistical procedure which yields the correlation coefficient referred to as r (-1.00 to +1.00) and involves the actual values, rather than the ranks (rank order) of the measurements. (05 Mar 2000) |