If we have a research design with only scale variables, we have two choices about how to analyze the data. The only question we have to answer is: Does the research question pertain to an association (or relation) between two variables or does it pertain to the degree to which one variable predicts the other? If the research question is about association, then we choose the Pearson correlation coefficient. If it is about prediction, then we choose regression. The decisions for category 1 are represented in Table E-1. (Note that the relation must be linear.)
| Research Question: Association (Relation) | Research Question: Prediction |
|---|---|
| Pearson correlation coefficient | Regression equation |