August 02, 2009
A coin flip isn't random
Most people believe that a tossed coin has a 50-50 chance of landing heads or tails.
Long story short: It's 51-49, with the more likely outcome being the side facing up when it was flipped.
A Reliable Randomizer, Turned on Its Head
In the Physics of a Coin Toss, It Turns Out, There's No Such Thing as 50-50 Odds
Coin tosses are a classic metaphor in economics for randomness. For instance, in his book about market efficiency, "A Random Walk Down Wall Street," economist Burton Malkiel compares the price movements of the stock market to the random outcome of a flipped coin: "[S]ometimes one gets positive price changes for several days in a row; but sometimes when you are flipping a coin you also get a long string of 'heads' in a row." According to Malkiel, mathematicians' term for a sequence of numbers produced by a random process is a random walk. To him, this is exactly what stock-price movements look like, hence the title of his book.
Similarly, Nassim Taleb, in "Fooled by Randomness," points out that the seemingly amazing success of money managers at beating the market is often best explained by pure chance. People misperceive patterns in what are, in fact, purely random sequences, akin to the outcomes of a coin flip. And as everyone knows, coin flips produce "heads and tails with 50 percent odds each."
Lately, the idea of randomness in stock prices has come under attack; prices for individual stocks (but not the market on the whole) often show small momentum effects: stocks that go up tend to keep going up, and stocks that are going down tend to keep going down. But the metaphor of a coin flip for randomness remains unquestioned. We use coin tosses to settle disputes and decide outcomes because we believe they are unbiased, with 50-50 odds.
Yet recent research into coin flips has discovered that the laws of mechanics determine the outcome of coin tosses: The startling finding is that they aren't random. Instead, for natural flips, the chance of a coin landing in the same position as it started is about 51 percent. Heads facing up predicts heads; tails predicts tails.
Three academics -- Persi Diaconis, Susan Holmes and Richard Montgomery -- made an interesting discovery through vigorous analysis at Stanford. As they note in their published results, "Dynamical Bias in the Coin Toss," the laws of mechanics govern coin flips, meaning that "their flight is determined by their initial conditions."
The physics and math behind this discovery are complex. To understand more about flips, the academics built a coin-tossing machine and filmed it using a slow-motion camera. This confirmed that the outcome of flips is not random. The machine could produce heads every time.
When people flipped the coin, results were less predictable, but there was still a slight physical bias favoring the coin's initial position 51 percent of the time. The reason real flips are less certain isn't just that the force can vary, it's that coins flipped manually tend to rotate around several axes at once. They tumble over and over, but they also spin around and around, like pizza dough being twirled. The more a coin spins, the more unpredictable the outcome.
I spoke to Holmes, one of the Stanford researchers, about this. She told me that when most people hear about this weird finding, they think it has something to do with the density of the coin, but she was able to disprove that by constructing a coin made out of balsa wood on one face and metal on the other. It made no difference come flip time. The dynamics of the coin flip, and its outcome, are determined not by the lack of balance in the coin but instead by the physics of spinning and flipping.
I asked Holmes whether coin flips used for, say, football, should be eliminated because they are biased. The answer is no, as long as the person calling the flip doesn't know how the coin is going to start out. In football, the tosser is never the caller; the tosser is supposed to be a referee. But if you are both the caller and the tosser, well, that changes things. Knowing about the bias in coin tosses give you an edge, albeit a tiny one.
Certain people, however, can make a toss come out heads (or tails) 100 percent of the time. Diaconis, Holmes's co-author and husband, is one of the people with this rare talent. Before becoming a mathematician, he was a professional magician. So how exactly is Diaconis able to make a coin toss come out a certain way? Holmes won't tell me: "It comes from his previous career -- it's magic."
You can read the first chapter here.
Free, the way we like it.
Snow Leopard next month — w00t!
I just saw over at Amazon that Snow Leopard (Mac OS X 10.6) is now available for pre-order for $29.
That's all well and good but what got me all atwitter and made my heart flutter was this: "Official release date has not been announced by Apple, though they have indicated this product will be released sometime in September."
Why am I so excited?
Because as a card-carrying TechnoDolt™ I wouldn't buy a computer with an OS that I needed to upgrade: it needs to be native.
I'm still using 10.3.9 on my 2005 G4 PowerBook and let me tell you, the SBBOD are more painful (and frequent) every day.
As soon as I can buy a MacBook Pro or iMac running 10.6 right out of the box, well, I'm so there.
Now it appears it's sooner than I'd thought (I'd heard October).
Bonus: I read somewhere that among the new features of Snow Leopard is Force Quit for a single page running within a browser rather than having to shut down the whole browser and all the pages open within it.
I cannot tell you how much better that single feature alone will make my daily life.
I'm very, very stoked.
Can you tell?
Pro Player Connect now lets fans join
Wrote Hannah Karp in the July 29, 2009 Wall Street Journal, "Pro Player Connect, a social-networking site for professional athletes that verifies players' identities using their driver's licenses, is now letting fans join. The site is also helping its 900 athlete-users link their pages to their true Facebook and Twitter accounts to foil imposters who pose as athletes on the internet. 'My information's on a lot of sites that I've never been on,' says New Orleans Saints long-snapper Jason Kyle, who started the site."
Nobody knows you're not an athlete on the internet.
Dual-voltage travel humidifier is so compact you can take it anywhere.
Get a better night's sleep by controlling the humidity of the air in your hotel room.
No tank — this Swiss-made, lightweight, portable humidifier generates a superfine cool mist that penetrates dry and irritated nasal, sinus and throat passages, using ultrasonic vibrations and regular tap water from any water bottle.
Features include whisper-quiet operation, mist output control, automatic shut-off, and low water indicator.
Includes 100–240V AC adapter for worldwide use, adapters for bottles from the U.S. and abroad, and travel case
4" x 3¼" x 2¾".
How to get someone under 20 to return your call
Call them, then hang up.
Bluebell chest of drawers
$14,700 to order.
TweetMic for iPhone
Long story short: 99 cent app lets you record your tweets — with unlimited recording time.
Wrote Tim Mercer in a July 27, 2009 Macworld.com review, "Instead of just the ordinary typed tweet, how about letting people actually hear what you’ve got to say? With Tweetmic from Voicetal, you can record and publish audio tracks, or 'tweetcasts,' directly to your Twitter account."
I wonder which band is going to be the first to use this app to get big?
What is it?
Answer here this time tomorrow.