Regression to the Mean

For today's Sunday reflection, this passage from a journal reviewer quoted in Gary Smith's "Standard Deviations":

"There are few statistical facts more interesting than regression to the mean for two reasons. First, people encounter it almost every day of their lives. Second, almost nobody understands it.
"The coupling of these two reasons makes regression to the mean one of the most fundamental sources of error in human judgment, producing fallacious reasoning in medicine, education, government, and, yes, even sports."

And speaking of statistics, this ;-):

"The average human has about one breast and one testicle."
-- Statistics 101