Fig. 6.

Examples of 3D ROC surfaces: (a) and (b) are surface representations for Gaussian distributions with r=0.5, ${\sigma }_1^2={\sigma }_2^2=3$, and r=0.5, ${\sigma }_1^2=1,{\sigma }_2^2=3$, respectively. (c) and (d) are grayscale representations of (a) and (b), respectively.