10. Of course, both differences may reflect both nature and nurture.
11. It is possible that genetic differences may also (or instead) be reflected by differences in variability in the groups. Thinking about such differences, however, also requires thinking about some sort of measure (e.g., the standard deviation or the interquartile range) as a signal reflecting the typical variability in a group.
12. However, we should note that in the Bright and Friel (1998) study cited earlier, the two distributions were non-overlapping, yet students did not use averages to compare them.