So far, you have been reading about statistics that describe sets of data. In many research studies, psychologists might want to know the extent to which two variables are related. Correlational statistics do just that.
Correlational statistics yield a number called the coefficient of correlation .
The coefficient may vary from 0.00 to 1.00. Correlations may also be either positive or negative. In a positive correlation, scores on two different variables increase and decrease together. For example, there is a positive correlation between high school average and freshmen grade point average in college. In a negative correlation, as scores for one variable decrease, they increase for the other variable.