That Random Coin Toss? Not So Random Afterall...

from the a-weaker-man-might-be-moved-to-reexamine-his-faith dept

One of my all-time favorite scenes in a play and movie, is the scene in Tom Stoppard's Rosencrantz & Guildenstern Are Dead where every coin toss comes up heads, leading to a bit of a philosophical discussion on probability. Of course, the randomness of the coin toss is the quintessential example of a random event and is used regularly for a variety of situations in which randomness is required, let alone expected. Except... it turns out the common wisdom may be wrong. Paul Kedrosky has the news of a test that showed that if you ask people to try flip a coin and get more heads than tails, they will, and not by a small margin either. In the test, 13 people were asked to flip a coin 300 times, trying to get as many heads as possible. All 13 participants got more heads than tails. Seven out of the thirteen had statistically significant margins of heads over tails (meaning almost certainly not a matter of chance). The highest was one individual had 68% of the coin flips land heads. In other words, a coin toss isn't particularly random.

Filed Under: coin toss, random


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  1. identicon
    Brandon, 13 Dec 2009 @ 7:29am

    Defining Randomness

    The problem with the coin toss is its actually not random at all, if you understand what randomness is really all about. Flipping a coin, by nature, is a completely non random event - all possible outcomes are strictly set, the odds of which are perfectly known. Randomness is unexpected and unpredictable with unknown outcomes - a coin toss could be random, if somehow the coin lands on its side or gets destroyed somehow I would call that outcome random.

    I suggest reading "The Black Swan" by Nassim Nicholas Taleb, or his previous book "Fooled by Randomness" probably the only guy who can explain this idea correctly. In it you'll discover that even gambling in a casino is completely non-random, it's fixed, we all know that. The randomness that effects casino's are truly random events such as entertainers getting mauled by tigers. (The biggest losses in casino history have been true random events, such as being robbed, or the classic Sigfried and Roy tiger mauling at the Mirage, which resulted in huge losses)

    So remember - randomness is unpredictable, with an unknown set of possible outcomes. Flipping a coin is almost the opposite of randomness, its the kind of predetermined experiment that you'll rarely find in nature.

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