Partial Correlation

A partial correlation is a measure of the relationship that exists between two variables after the variability in each that is predictable on the basis of a third variable has been removed. A partial correlation, like a conventional Pearson product-moment correlation, can range from -1 to +1, but it can be larger or smaller than the regular correlation between the two variables. In fact, a partial correlation is simply a conventional correlation between two sets of scores. However, the scores involved are not the scores on the original variables but instead are residuals—that is, scores reflecting the portion of the variability in the original variables that could not be predicted by a third variable.

As a concrete example, a researcher might be interested in whether depression ...