[jonkelly]

My favorite related demonstration is to do a "tournament" where you start with 64 people and eliminate the 1/2 who don't flip heads each round. Some "amazing" flipper will get through 5 to 7 rounds and win. Something to think about when you see a mutual fund manager who beats the market 7+ years in a row.

[Estragon]

There's a con based on this: send half your marks a prediction that the stock market will go up next week, and half a prediction it will go down. Repeat next week, restricting to whichever set received the correct prediction. After five weeks, you'll have a group of people who think you've accurately predicted stock market movements for five weeks in a row, and some of them will be prepared to pay for your next prediction.

[billmcneale]

I remember reading this anecdote to explain the anthropic principle:

http://beust.com/weblog/2010/08/17/fun-with-the-anthropic-pr...

[hobbsy]

This reminds me of Derren Brown's The System: http://en.wikipedia.org/wiki/Derren_Brown#Derren_Brown:_The_...

[eridius]

Do you watch Leverage too?

(Leverage is a TV show in its 4th season, and last week's episode included this very con http://www.tv.com/leverage/the-boiler-room-job/episode/13919...)

[jonkelly]

That's really pretty neatly evil, I hadn't heard of that.

[EvanKelly]

I have always liked to think of an international Rock-Paper-Scissors competition where everyone in the world participated.

One person in the world would win all of their matches in a row.

[jws]

…and only play 40-60 rounds. Logistics aside it would be over in 5 minutes.

[Luc]

That's not quite comparable I think, with RPS being a game of skill and all.

[guygurari]

It's not true that 1/2 the players will flip tails each round, or that there will necessarily be one winner. In fact, if you go 7 rounds with 64 people there's a 60% chance that no one will flip all-heads.

[jonkelly]

Yep, I should have said _about_ 1/2, but that's why I said 5 to 7 rounds. Even 5 straight wins produces the illusion of skill.