The random coin toss must be one of society’s most frequently used decision-making mechanisms. We use the coin toss to choose which movie to see, to determine team positions in major sporting events, to divvy up household chores, and even name cities. But it may be that the the random coin toss isn’t so random. A 2007 study found that a vigorously flipped coin is likely to land on the same side it started on at least 51 percent of the time, possibly more depending on the person doing the flipping. (HT: Chris Blattman)[%comments]
Not So Random After All
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They don’t just flip coins at most games because everyone knows the flipper can control the outcome. They let the coin fall and bounce. They usually now call it a coin toss for that reason.
With some practice, a good slight-of-hand magician can flip a coin and consistently get whatever face s/he wants.
Different weight on each side because of the engraving is also a source of bias.
Coin flipping is notoriously manipulable, and is a terrible randomizing device. Makes you wonder why the NFL depends on it for overtime games, since the first team to get the ball has a much higher rate of winning.
Refer to papers by Diaconis and Engel as well as chapter 10 in Jaynes (“Physics of ‘random experiments’” Probability theory: the logic of science)
Manipulation by the flipper shouldn’t be an issue with the flipper is an independent third party (like a referee). And letting it bounce off the ground probably helps too.
Isn’t any advantage negated by having one person flip, and the other person call it in the air? This would be true even if the flipper had 100% control over which side landed up, because he wouldn’t know which side his opponent would choose until after he had flipped it. (Effectively, this would just turn the coin toss into the game “odds and evens.”)
come on Walt, if the coin flip was really that unfair wouldnt all teams pick the higher outcome everytime? and which one IS the unfair outcome? In a game of inches, where the home team is already at a significant advantage and the outcome of one pass tipped in the air adds far more variance to the outcome than the coin flip I dont think it is a problem at all in the NFL. I am more concerned about the silly roughing the passer rules!
It would be fun to see the success rate of the visiting team correctly calling the toss through NFL history… my bet is that it is pretty close to 50.000%
Nothing beyond the realm of quantum physics is truly random.
“Makes you wonder why the NFL depends on it for overtime games, since the first team to get the ball has a much higher rate of winning.”
Except, of course, they don’t. It’s about 52-48.