Principal axis analysis of dental attrition data



The principal axis method is an age independent analysis method for dental attrition data which avoids many problems associated with earlier methods of analysis, correlation and regression. A principal axis equation is determined from the scatter of M1 on X and M2 on Y, and the slope of the equation can be used to indicate rate of wear. High slopes indicate rapid rates of wear. Because rate of wear rather than degree of wear is the parameter of interest, the procedure is age independent. Confidence regions can be calculated to test the distinctness of the slopes. Dental data from three Amerind skeletal samples, Indian Knoll, Hardin Site and Campbell Site, are used to illustrate the technique. Because least squares fits such as the principal axis solution are strongly influenced by the magnitude of variance in the data, two different methods of ordinal data collection are used in this test: Molnar's 1–8 and Scott's 4–40 scales. The Scott scoring system provides more satisfactory results when used in the principal axis analysis technique because of smaller confidence regions. The testing of the technique on other samples is urged.