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. Author manuscript; available in PMC: 2013 Nov 12.
Published in final edited form as: J Thorac Cardiovasc Surg. 2012 Jul 24;145(4):10.1016/j.jtcvs.2012.06.029. doi: 10.1016/j.jtcvs.2012.06.029

FIGURE E1.

FIGURE E1

The relationship between the number of categories and the degree of within-category homogeneity. Within-category homogeneity is defined as 1 minus the ratio of within-category variance to total variance of procedure-specific morbidity estimates.