a) Hypothetical relationship between the best fit power law slope and the lower limit (xmin) for a stable power law fit. The flat region in the middle of the plot shows the range over which the fit is independent of the choice of xmin, i.e. stable. b) The same relationship as a) for the real GOES long channel peak flux frequency distribution derived with the standard GOES event list (start threshold = 40%, end threshold = 50%). It can be seen that there is no flat region where the power law slope is independent of choice of xmin. This suggests that the distribution may not be best approximated by a single power law.