In the general sense, any method to study association, interdependence, or relationship between variables (Pimentel, 1979). Correlation and regression analyses (see below) use similar computations, but are not the same. Correlation has no distinction between dependent and independent variables (they are best referred to as Y1 and Y2, rather than X and Y), whereas regression lends support to hypotheses of possible causation of changes in Y by changes in X (called the dependent and independent variables respectively), for purposes of prediction of Y in terms of X and for purposes of explaining variation in Y in terms of X (Sokal and Rohlf, 1981).