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
    Chad, 13 Dec 2009 @ 5:56pm

    Flipping a coin is NOT random if you pay attention to all of the variables at work. The position the coin is in before it is flipped, the number of "flips" the coin does in the air, the result of the coin after that number of flips.

    In fact, if you were to know those variables, you could predict the outcome 100% of the time.

    1. Coin is on heads
    2. Coin flips 4 times in the air.
    3. Catch the coin and do the smacking on the back of your hand
    4. Result will be tails. Every time.

    If the coin only only made 3 flips, it will be heads. If the coin made 5 flips, it will be tails.

    To full keep things random, the person flipping the coin must NOT be aware of what position the coin is before flipping, and they must NOT be able to manipulate or predict the number of flips it would make in the air.

    A "coin toss" program in a computer will always be fully random because it does not take these variables into account. Since humans can, of course it's not fool proof.

    Calling 68% extremely predictable though........ I don't know if I agree with that in any case. Keep in mind that as unlikely as it is that all outcomes will be heads, it's still theoretically possible for it to happen. It may have been just as likely to be 68% tails. Come back to me when it's 90%.

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