# Going for a Sweep in Game 3

I’ve been watching a fair amount of SportsCenter / BBTN today, and every two minutes someone mentions that there are “seven teams going for a sweep in an interleague series!”, as if this is some sort of big deal. There are fourteen interleague series this weekend. If every match were a coin-flip, wouldn’t we expect exactly seven teams to be going for sweeps in the third game of a series?

We’ll start by assuming each team has an equal probability of winning each game, and the results of each game are independent. After one game, you’re guaranteed that one team will have a 1-0 advantage. There is a 50% chance that the team that won the first game will win the second, meaning that there is a 50% chance the series will be 2-0 after two games. Therefore, dak is correct, you would expect half of the series to be on the verge of a sweep.

Why did the media make a big deal out of this — and, I can confirm dak’s observation: this was a big deal on SportsCenter and Baseball Tonight — if it’s actually expected? Because they don’t understand basic probability. In fact, they are overtly antagonistic toward understanding simple logic and math. That’s why websites like Fire Joe Morgan are so much fun to read. Media stupidity is such an easy target, and, even when their stupidity is pointed out them, they show no interest in correcting their errors or remedying the problem. It’s like dealing with creationists.

1. #1 J-Dog
June 23, 2008

Can we do MORE than Fire Joe Morgan???!!! This guy is such a complete and utter moron that firing him seems way too easy.

2. #2 razib
June 23, 2008

if sports reporters didn’t say stupid stuff they’d have little to say. stupid analysis make for more readable narrative than probability distributions.

June 24, 2008

That paragraph actually tripped me up for a minute. I don’t know how to explain it, but it just seems wrong. 50% going for sweeps? No way.

After I’d thought about it for a moment it even took me a second to realize the error in my analysis. I thought “no, it’s 3.5 series” until I realized that it doesn’t matter which team is going for the sweep.

Then I felt ashamed that a sports journalism blog had so confused me. I still <3 FJM.