Set of 20 distributions of electron onset times as a function of data integration time using STEREO-A / SEPT 55-65 keV electron data from the April 17, 2021 SEP event. Each distribution consists of 1000 possible onsets, and its mean, median, and mode are marked in the plot with a yellow circle, red triangle, and a blue pentagon, respectively. The purple and blue areas mark the times that bound ~68 and ~95% of the distribution.