Correlation is a measure of the linear relationship between two variables. The Pearson Product Moment Correlation Coefficient, represented by r, ranges from +1.00 for a perfect positive relationship to -1.00 for a perfect negative relationship. If there is no linear relationship, r=0. Thus, r indicates both the direction (positive or negative) and the strength of the linear relationship (e.g., weak or strong).

If a relationship is nonlinear, then simple r and regression may not be the appropriate model.

Your instructor, textbook, or software package may use different terms than those used in the tutorial. Below we provide a listing of alternate terms.

*SS Total: *Total variance, SS Corrected Total (SAS)

*SS Error: *Error variance, Residual variance, SS Residual (SPSS, SYSTAT)

*SS Predicted: *Explained variance, SS Regression (SPSS, SYSTAT), SS Model (SAS)

*R-Squared: *Coefficient of Determination