Visualization of SRD ranking and grouping. Average was used as reference. Scaled SRD values (between 0 and 100) are plotted on the x axis and left y axis. The right y axis shows the relative frequencies for the fitted Gauss curve on random numbers (black) (XX1 = 5% error limit, med = median, XX19 = 95% limit). If an SRD value (similarity metric) overlaps with the Gaussian curve, it is not distinguishable from random ranking.