[imagesource:flickr]

Someone might need to send Siya Kolisi this article before our match against France because it turns out the seemingly ‘fair’ odds of a coin toss are not so fair after all.

After crunching the numbers and examining an astonishing 350,757 coin tosses, a group of researchers led by American mathematician Persi Diaconis discovered that coin tosses are not really random after all. And you can even slightly change the odds in your favour.

We assume that tossing a two-sided coin in the air would give you a 50/50 chance (or one in two) of calling it correctly, but according to the tossing team, the action of flipping the coin introduces a slight wobble, which has an effect (if only tiny) on the coin.

The tossers reported their findings in a publication that has not yet undergone peer review, stating that: “According to the Diaconis model, precession causes the coin to spend more time in the air with the initial side facing up – Consequently, the coin has a higher chance of landing on the same side as it started (i.e., ‘same-side bias’).”

Diaconis found that coins land on the same side they were tossed from around 51 percent of the time. The team recruited 48 people to flip 350,757 coins from 46 different currencies, finding that overall, there was a 50.8 percent chance of the coin showing up on the same side it was tossed from.

Now you may not think .8 per cent is that much, but keep in mind that prizes and even the odd inheritance have been decided this way.

Further tossing revealed that the results of coin tosses ‘vary greatly between individuals, with some exhibiting a large same-side bias and others having none at all. This suggests that the outcome of coin tosses may (somewhat) depend on the tosser.’

“The magnitude of the observed bias can be illustrated using a betting scenario,” the team explains in their discussion. “If you bet a dollar on the outcome of a coin toss (i.e., paying 1 dollar to enter, and winning either 0 or 2 dollars depending on the outcome) and repeat the bet 1,000 times, knowing the starting position of the coin toss would earn you 19 dollars on average.”

Unfortunately, not everyone gets to flip the coin, so the researchers suggest that when coin flips are used for serious betting, the coin’s starting position needs to be concealed. That way the one calling the toss is blind to the possible outcome. That seems more fair.

And just in case you’re the kind of person who used to stay up late to watch Big Brother, here’s a full-length video of the epic coin-tossing marathon:

[source:ifls]