Fig. 3.

Approximate AUC with Gaussian distributions. (a) The AUC using Gaussian distributions for the same values of S and B as used in Fig. 1(c). (b) The relative error of this approximation (defined as $\text{(AU}{\text{C}}_{\text{Gauss}}-\text{AU}{\text{C}}_{\text{Poiss}})/\text{AU}{\text{C}}_{\text{Poiss}}$ ) is shown for various values of S and B. Nearly all errors are small except when S and B are small, assuming $S$ is finite.