Significance tests and concepts of degree of preferred orientation applied to three-dimensional orientation data have been discussed many times (Stauffer, 1966; Voll, 1960; Flinn, 1958; Drescher-Kaden, 1954). These tests are based on some form of statistical correlation or on departures from some ideally random model. These tests tend to be too sensitive for comparison of diagrams which have an obvious preferred orientation, and vectorial summation methods are limited to simple preferred orientation patterns. For convenience, a “coefficient of degree of preferred orientation” needs to be a numerical value which can be simply and quickly derived from a contoured stereographic projection.
This note demonstrates that an empirical property of contoured stereographic projections of natural preferred orientation data can be used to derive such a coefficient.