Thursday, February 26, 2004

Revelation: Coin Tosses Obey Newtonian Physics

Am I missing something, or is this really as obvious as I think it is?

Feb. 24, 2004 -- Flipping a coin may not be the fairest way to settle disputes. About a decade ago, statistician Persi Diaconis started to wonder if the outcome of a coin flip really is just a matter of chance. He had Harvard University engineers build him a mechanical coin flipper. Diaconis, now at Stanford University, found that if a coin is launched exactly the same way, it lands exactly the same way.

The randomness in a coin toss, it appears, is introduced by sloppy humans. Each human-generated flip has a different height and speed, and is caught at a different angle, giving different outcomes.

But using high speed cameras and equations, Diaconis and colleagues have now found that even though humans are largely unpredictable coin flippers, there's still a bias built in: If a coin starts out heads, it ends up heads when caught more often than it does tails.

Color me underwhelmed by this report. A coin flipped in a given manner will land on the same side if tossed precisely the same way again? You're having me on! Even the bit about the slight bias we have in coin tossing strikes me as less than revelatory, as it's long been known that humans are terrible at randomness, even when explicitly trying for it.

Persi Diaconis is a very smart guy (and that's putting it mildly) so there's got to be more to the story than is being let on here, but a visit to his web site gives no evidence of a recent paper covering this issue. What's stranger still is that the reporter for the story, David Kestenbaum, has a PhD in physics from Harvard, so it ought to have been blazingly obvious to him too.