# 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

1. Anonymous Coward, 11 Dec 2009 @ 7:07pm

### Re:

Exactly, that's why I always contended that heads has a slightly better chance of winning, because there seems to be slightly more weight on tails just by the curvatures, though it's a very very slight difference. If you flipped the coin, without trying to influence it, the chances of getting heads vs tails maybe almost 50/50 but if you flipped the coin many many times it may show a bias.

This is why in statistics they always say, "if you flipped an unbiased coin" or "if you rolled an unbiased die" they have to add that word unbiased.

In fact, I knew people that used to be able to manipulate how the dice rolled and they seemed very good at getting it to roll however they wanted. They made money just making bets with others on how the dice will land as well. Of course no one would ever admit that they were manipulating the dice but these people were very coordinated and after watching them for a while it becomes somewhat obvious. Then again, they only played for a few dollars, it wasn't worth making an issue about.

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