Correlation coefficients summarize the strength and direction of a linear relationship between variable.
Direction describes whether there is a positive or negative relationship between the variables.
For instance, there might be a positive correlation between calorie intake and weight. And a negative correlation between the number of beers you have before a test and your score on the test. The strength of the correlation describes how well you can predict one variable knowing the other. The most common correlation coefficient is the Pearson Product Moment Correlation. This is often symbolized by an r .