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
