The second approach uses the distributions of the standard deviations of predictions to estimate the number of erroneous retention times. The filled part of the plot (Figure ) describes the difference between groups with 0 and 5 "yellow cards" . The density function for the group with 5 "yellow cards" can be considered a superposition of two major distinct distributions: ordinary retention times (present in the group with 0 "yellow cards"), and inaccurately predicted ones (mostly present in the tail of the distribution).