The simplest way to reveal a possible correlation between bivariate data is to express it graphically. Let's use the example from the preceding page:
Apparently there is a strong linear relationship with the points, one that follows an upward moving pattern. If we were to join the points with a line, it would possess a positive slope, representing a positive relationship. Other examples of scatter diagrams help illustrate relationships between points.
Scatter diagrams are helpful in that they do not require complex calculations. A more precise method of discovering a relationship is to make apply the linear correlation coefficient
Linear Correlation Coefficient