Coin toss is proven biased after all

One of the most trusted and long-standing even bets in history, the humble coin toss, has now been proven biased. That is, choosing heads or tails is not a 50-50 chance if you first get to see which side of the coin is facing upward before the toss.

The remarkable claim comes from Stanford University mathematics professor Persi Diaconis.

One way of thinking about this, as noted in an article from Coding Wheel, is to look at the ratio of even and odd numbers starting from one. What you’ll discover is that no matter what number you stop at, there will never be more even numbers than odd numbers in that sequence. The coin flips work in much the same way.

Prof Diaconis first realised that coin flips were not random after he and his colleagues managed to rig a coin-flipping machine to get a coin to land heads every time.

He and his team then asked human subjects do the same thing over and over, recording the results with a high-speed camera. Though the results were a little more random, they still ended up with the 51-49 per cent margin.

ie: 51 out of 100 coin tosses, the coin will land with the same side facing upwards as before the coin was tossed.

Prof Diaconis noted that the randomness is attributed to the fact that when humans flip coins, there are a number of different motions the coin is likely to make.

For instance, he showed how coins don’t just move end to end, but also in a circular motion, like a tossed pizza.

He also found that there are ways to flip a coin where it looks like it is tumbling in the air, but in reality, it doesn’t move at all.

Prof Diaconis proved this by tying a ribbon to a coin and showing how in four out of 10 times the ribbon would remain flat after the coin was caught.

Source: News.com.au | Flipping a coin may not be an even bet after all 

This little fact, however minute an advantage it might provide, might do well to be remembered by sports stars and betting folk.

A die was not considered in this study, but it stands to reason that the same “starting side up” minuscule advantage may also apply under certain conditions.

 

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Categories: Science, Technology

Author:Andrew Beato

CEO, Chief Editor and founder of Intentious. Passionate comment enthusiast, amateur philosopher, Quora contributor, audiobook and general knowledge addict.

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2 Comments on “Coin toss is proven biased after all”

  1. December 4, 2012 at 9:42 pm #

    With everything else going on around us, this is probably something we would have been better off having never known, if the conclusion is even definitive. Diaconis wasn’t paid more than a quarter for this, right?

    • December 5, 2012 at 12:31 pm #

      Can’t all be hard-hitting massive controversy all of the time 🙂 It would wear the morality centre of my brain out!

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