The strength of this method lies in the fact that it can be used to determine if there is a relationship between two variables without having to directly manipulate those variables. In other words, correlation can be used when the experimental method cannot; correlation can be used when it is impractical and/or unethical to manipulate the variables.

Correlation also can be used as a basis for prediction. For instance, if we know that two variables are highly correlated, say +.85, we can predict the value of one by knowing the value of the other. Suppose that SAT scores and college GPAs (grade point average) correlate at +.85. Knowing this, college admission officials can predict a student's grades in college, with a fair degree of accuracy, if they know that student's SAT scores.