# 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. Derek, 12 Dec 2009 @ 1:59pm

### coin Tossers

Although I have a day job as a Network Administrator, I have been a professional magician for over 25 years. Repetitive coin tosses WILL have a strong bias to either heads or tails. Once the person tossing, gets into a familiar rythm for tossing the coin they will replicate their actions with surprising accuracy. The strength of the toss, the height of the toss etc etc all being very very similar each time will result in the coin landing back in the hand the same way a great number of times. I learned to control the toss of a coin at an early age in my magic career. A better control would be to have 300 people toss a coin and allow it to land on the ground, the result being noted by an independant observer. I believe this would result in a more even spread of heads and tails.

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