Compute the eigenvalues for the correlation matrix and plot the values from largest to smallest. Examine the graph to determine the last substantial drop in the magnitude of eigenvalues. The number of plotted points before the last drop is the number of factors to include in the model. <ref>{{Cattell, R. B., & Jaspers, J. (1967). A general plasmode (No.30-10-5-2) for factor analytic exercises andresearch. Multivariate Behavioral Researchmonographs, No. 67-3}}</ref> <ref>{{Catell, R. B. (1966). The scree test for the number of factors. Multivariate Behavioral Research, I, 245-276.}}</ref> This method has been criticized because of its subjective nature (i.e., there is no clear objective definition of what constitutes a substantial drop). <ref>{{Kaiser, H. F. (1970). A second generation little jiffy. Psychometrika 1970; 35: 401-415.1972-07976-001}}</ref>
