Coin tosses can be easily rigged: study

December 7, 2009

The ubiquitous coin toss is not so random after all, and can easily be manipulated to turn up heads, or tails, a Canadian study has found.

Used for centuries to settle feuds, start sporting matches, decide an uncertain course of action, and even as a randomization tool in some research studies, tosses were thought to be impartial arbiters.

Not so, say researchers at the University of British Columbia in westernmost Canada who found that the outcome of a can actually be influenced with minimal training.

They asked 13 ear, throat and mouth (otolaryngology) residents in Vancouver to each flip a coin 300 times to see if they could bring up heads.

All of the participants achieved more heads than tails, with 7 of the 13 coming up with "significantly more heads" than tails, said the study published in the current December 7 issue of the (CMAJ).

One of the participants was able to achieve heads 68 percent of the time.

Success depended on how high a coin was tossed, how quickly it was tossed it, how many times it was spun and how it was caught.

"This study shows that when participants are given simple instructions about how to manipulate the toss of a coin and only a few minutes to practice this technique, more than half can significantly manipulate the outcome," the researchers wrote.

The study was included in the CMAJ's annual Christmas holiday review of offbeat research.

Other CMAJ highlighted studies found:

-- a link between rain and medical school admissions. Students interviewed on rainy days received a one-percent lower score on admissions tests than those on sunny days, suggesting mood plays a part in selection;

-- quarantine and cure would only delay the inevitable spread of a zombie outbreak. A was created for just such an unlikely occurrence;

-- and public health officials must come up with scarier names for viruses in order to frighten people into taking preventive health measures to curb epidemics.

"H1N1 sounds like the name of an income tax form or a robot that might hang out with R2D2 in Star Wars," said researchers. "Compare this to the Black Death.

"If public health physicians want people to live, they must learn how to scare them to death."

(c) 2009 AFP

Explore further: Bluffing could be common in prediction markets, study shows

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jerryd
3 / 5 (2) Dec 07, 2009
The rates they claim are in the probability range. Notice 50% achieve higher rates of head which means 50% would hit tails too.

The 7 out of 13 just means one or the other had to be ahead as it was an odd number.
x646d63
5 / 5 (2) Dec 07, 2009
@jerryd, I don't think you read it correctly:

All of the participants achieved more heads than tails, with 7 of the 13 coming up with "significantly more heads" than tails


It's unlikely that chance would have all 13 flip more heads than tails, but that was the case.
Adrianrain
3 / 5 (2) Dec 07, 2009
I use a trick all the time and it works for me. If i need to flip a coin and i want it to be heads for example. I will keep flipping it till i get two tails in a row then I will go out to where I have to go and flip it again. Three tails in a row is hard to get but two tails followed by a heads seems easier.
jonnyboy
3 / 5 (2) Dec 07, 2009
Adrainrain. instead you should be trying to flip heads until you figure out what speed and how high to toss it. What you are describing would work about as well as spinning around in a circle twice to the right and then once back to the left.
axemaster
5 / 5 (1) Dec 08, 2009
Adrainrain... each flip is independent of the others, so no matter what you do beforehand, that 3rd flip will always be 50/50 chance.
dammy
Dec 08, 2009
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BetaSki
not rated yet Dec 08, 2009
This really is not very shocking, although it may confirm previously simply paranoid fueders. Of course, the standard procedure for preventing this kind of tampering is the "call it in the air" method.
ennemkay
not rated yet Dec 08, 2009
awesome study. the best technique: the two-headed coin. i think adrianrain was joking?
KBK
1 / 5 (1) Dec 08, 2009
It is a physical system with input from the, ur, eh.....tosser. Physical input that, for the larger part, becomes the entire energy input.

Furthermore, the termination of the 'game' or toss, is controlled by the person initiating the entire physical aspect of energy input (begin)to reach the conclusion of the 'toss'(end).

Therefore it ~CAN~ be successfully 'gamed', or altered from any random character.

I've known this for years. And my personal best is heads 168 times in a row. Not short tosses or low energy input with low numbers of revolutions. About2 feet in height on average and a fast spin of about1.5 seconds in length. It's all in the initial energy input..and the TIMING of the toss. Listen to the 'ring' of the coin..it has to be ~Just right~. use the same coin every time.

As for timing issues, the best drummer, on record, using a click track, can come down on the beat REPEATEDLY..at 100,000th of a second. He's known as the 'human metronome'. Look it up.
ricarguy
2.3 / 5 (3) Dec 08, 2009
I like the mathematical model about the zombie outbreak the best. One can create a model to show most anything you want. Just ask Michael Mann. LOL
bfast
not rated yet Dec 08, 2009
Jonnyboy, "instead you should be trying to flip heads until you figure out what speed and how high to toss it."

BetaSki, "Of course, the standard procedure for preventing this kind of tampering is the "call it in the air" method".

KBK, "I've known this for years. And my personal best is heads 168 times in a row. Not short tosses or low energy input with low numbers of revolutions. About2 feet in height on average and a fast spin of about1.5 seconds in length. It's all in the initial energy input..and the TIMING of the toss. Listen to the 'ring' of the coin..it has to be ~Just right~. use the same coin every time."

KBK, I don't buy it.

That said, I have a 100% call success rate. You can call it in the air, and I still will produce the opposite of your call. I flip the coin in the air, snatch it out of the air, and place it on my opposite forearm. Thats how I was always taught to do a coin toss. Once I have grabbed the coin, I feel it with my finger, and present my choice
Yes
not rated yet Dec 08, 2009
Students interviewed on rainy days received a one-percent lower score on admissions tests than those on sunny days, suggesting mood plays a part in selection;

1 percent out of one hundred? Now you see evidence that the writers of this article do not understand much about statistics. Unless they had a million test persons, this says nothing. And even then I would say 5% for drawing conclusions
qwelkjhe
not rated yet Dec 09, 2009
http://en.wikiped...el_Bluth

^ That's your human metronome. Pretty silly.
PeterROwen
Dec 14, 2009
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