When the scatterplot displays a linear relationship, we supplement it with the correlation coefficient (r), which measures the strength and the direction of a linear relationship between two quantitat...When the scatterplot displays a linear relationship, we supplement it with the correlation coefficient (r), which measures the strength and the direction of a linear relationship between two quantitative variables. It is a third variable that is neither the explanatory nor the response variable, but it affects your interpretation of the relationship between the explanatory and response variable.
