A Geometric Interpretation of Partial Correlation Using Spherical Triangles

This article shows how spherical triangles may be helpful in interpreting and visualizing the relations between partial and simple correlations. The formula giving the partial correlation coefficient in terms of the pairwise simple correlations is seen to be identical with the fundamental formula of spherical trigonometry. The spherical representation is applied to illustrate the masking effect of one variable on another in multiple linear regression.