Regression Toward the Average by Austin Peterson (blog entry 3)

Regression Toward the Average is something society as a whole shows in many ways but sports I think offers the greatest example. In sports many time when a player is doing something spectaculor over and over again he is praised but then when he returns to his normal abilities they call it “coming back to earth”. Regressioin Toward the Average is the statistical tendency for extreme scores or extreme behavior to return toward ones average. Few things show this principal better than sports.

I hinted in my intro that this theory was shown in sports and that is where my mind went as soon as I better understood the concept. This link is to Derek Jeter postseason statistics ( and shows a terrific example of a great player who started hot and has now regressed toward the average in his sport. A must forpeople who show regression toward the average is that their original test/performamce must be a very high score and set a very high standard for themselves. Typically one far greater than their abilities and one far above the average for that situation.

Derek Jeter was a great example of this, in his first two playoff sereis he hit over .400 and in 6 of his first 9 he hit over .333 both are exceptional numbers and far above the average that is to be expected out of a player in the playoffs. But now we sit and Derek Jeter has had 15 years and 31 series of expierience his numbers have come back to hig average. His career postseason average is just above .300 which matches up nicely which his 18 year career average which was just above .310.

Derek Jeter was the wonder kid who did the unexpected but as he continued to play and even play well because his start was so great his stats had no choice but to regress toward the average. This example shows how even with great players they all will come back to their average at some point.

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