How to flip a coin

by on October 24, 2009 at 11:03 pm in Games, Science | Permalink

Chris Blattman reports:

Using a high-speed camera that photographed people flipping coins,
the three researchers determined that a coin is more likely to land
facing the same side on which it started. If tails is facing up when
the coin is perched on your thumb, it is more likely to land tails up.

How much more likely? At least 51 percent of the time, the
researchers claim, and possibly as much as 55 percent to 60 percent –
depending on the flipping motion of the individual.

The original research is here.

1 rob October 24, 2009 at 11:17 pm

this would make a difference if coin flipping were ever subject to the law of large numbers, but is it? probably never.

2 Joey October 25, 2009 at 12:42 am

The real result from that work is that a massive advantage can be gained if you spin the coin (like a top). Some coins will land “tails” ~80% of the time, because the weight distribution matters.

3 ranon October 25, 2009 at 2:00 am

A good candidate for the Ignobel prize.

4 Slocum October 25, 2009 at 7:13 am

“Why did they need a high-speed camera for this?”

That was my initial question, too. I assume that they didn’t just want to find out whether there was non-randomness, but also why. And — if there were individual differences where some people produced more biased results — what about the way they flipped the coin produced those biased results?

5 Cyrus October 25, 2009 at 7:54 am

This seems like an application of Benford’s Law in base 2.

6 babar October 25, 2009 at 8:20 am

what about that stats for people who flip real estate? how much of that real estate ended up landing on its tail? and why would anyone flip a coin? is it possible it could be worth more coming down than going up? is this because of deflation?

7 -- October 25, 2009 at 4:08 pm

From a ‘james franklin’ science of conjecture perspective, this could be a discovery of great merit, amongst others bah, bah, bah

8 Konstantin October 26, 2009 at 5:52 am

This is actually quite believable result, as flipping a coin requires an impulse applied to it, which increases height of flight and spinning speed at the same time, if more powerful. And those two can cancel each other out to some extent when counting how many revolutions a coin made before landing.
In reality probability bias should depend on actual person doing flipping, as initial movement of hand matters a lot, as well as catching height 🙂

9 Parke October 26, 2009 at 4:25 pm

Of course, good etiquette for coin flipping has somebody other than the flipper call heads or tails. Even without this research, I would not have gambled quarters against somebody who insisted on flipping and calling the choice.

10 Gögüs February 8, 2010 at 10:46 am

Nice article been told. Thanks to the previous effort.

11 Estetik April 24, 2010 at 2:14 pm

Of course, good etiquette for coin flipping has somebody other than the flipper call heads or tails. Even without this research, I would not have gambled quarters against somebody who insisted on flipping and calling the choice.

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