Fig. 1.

Relative error of SNR² estimators as a function of the total number of images, 2n. The plots assume p = 40 channels with SNR² = 0.12837 (left), 0.90987 (middle), and 3.2847 (right), corresponding to AUC values of 0.6, 0.75, and 0.9, respectively. The estimators are denoted as follows: θ̂₁ (circles), θ̂₂ (diamonds), θ̂₃ (triangles), and θ̂₄ (squares). The relative error (in %) is calculated as $(\sqrt{\text{MSE}}/({\text{SNR}}^2))\times 100$, where MSE denotes the mean-square error.