Note that we do not often use the mean to describe onset
times. The reason is that it is too much influenced by a few extreme
values.

note that the intervals in the above chart would really be
at least one-stage more precise than are shown here. For example,
"51-60" really means 51.00 to 60.99 (if we mean decimal hours) or 50:00 to 60:59
(if we mean hours and minutes)