Wednesday, June 8, 2011

Superstition

Dallas's comeback win last night brought the series back to 2-2, and is promising to make this an especially memorable finals. People have torn apart Lebron and Jason Terry's play, while praising Dirk and Dwyane Wade. Turns out though, sports reporters have missed the single best predictor in the series: whether or not I wear my old Mavericks jersey. I wore it for games 1 and 3, but not for 2 and 4. Clearly me not wearing the jersey corresponds exactly to Dallas winning. Is there something there? Or is this an example of me having to much time to think of wacky things now that finals are done?

Traditionally, statisticians use 5% as the probability cutoff for correlation. If there's less than a 5% chance something would happen randomly, they assume it's a non-random process. The chances that my fashion choices would correctly predict 4 games in a row is just 1/16, or about 6.3%. That's not statistically significant, but it's close. If my jersey gets one more game right however, the odds move to 3.1%, a level that actually is significant. I won't be wearing the jersey for game 5 (go Mavs!) so a Dallas win will be more than just an important finals game, it'll be validation for all who ever believed that their particular scrap of cloth influences their team's play.

*Okay, clearly my shirt doesn't influence the game. What's wrong with this analysis?
First, I set the null hypothesis halfway through. Flip a coin 5 times, then hypothesize those results happen, and your test will be significant. If I say my jersey is a predictor one way or another, it could predict a Dallas win or loss, so 6 games is the level of significance, not 5.

Second, correlation does not imply causation, so it's possible some non-random third party is influencing both. Maybe I put the jersey on only when Dallas is losing (subconsciously). Or maybe Dirk watches what clothes I wear and then plays accordingly just to mess with my head.
Finally, even if something happens only 3.1% of the time from random chance, a random distribution will still give that answer 3.1% of the time. If you have 32 octopi picking 5 games, one of them is probably going to pick all 5 right. Then you can name him Paul and get the whole world to watch him.
Nonetheless, even though it's not true, I still kind of believe in this stuff. The truth is, I won't be wearing the Nowitzki jersey for game 5 because I want Dallas to win. But I won't be placing bets on it.
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