Monday, September 17, 2012

Thinking Out Loud: Replacement Referees and Home-Field Advantage

Home-field advantage, like the Cubs' curse and the substandard jumping abilities of Caucasians, is one of those sports truisms that has been accepted for decades as a given. The 2011 book Scorecasting investigated this phenomenon and ventured to explain why home-field advantage still existed in the era of free agency, chartered jets, and five-star hotels. Consider this slideshow, taken from the presentation given by the authors at the 2011 Sloan Sports Analytics Conference:

Friday, September 14, 2012

Bad Beats: The Predictive Power of Past Years' ATS Record

Last week, I used this space to complain about losing money to my friend Dave by betting against Tulane football.

Faaascinating, I know. But it gives me a chance to make an Important Point about the predictive value of statistics.

My confidence in my bet was based on the fact that, from 2003 to 2011, Tulane covered just under 40% of their games against the spread. Winning 60 percent of your bets would make the average professional bettor salivate, so I was happy to bet based on this big trend.

There were two things I ignored: first, that one game is the smallest of sample sizes, and second, that past results are no guarantee of future performance. The second point is the interesting one, so let's focus on that: if a team has done better/worse than average against the spread in the past, does that tell us anything about its performance against the spread in the future?

Monday, September 10, 2012

Protecting the Investment: The Stephen Strasburg Decision

When I heard that the Washington Nationals had shut down Stephen Strasburg for the season, I thought I had a nice article for Monday all sewn up. I could find pitchers who had had Tommy John surgery, plot their innings in their first full season after the injury, and compare that to their WAR or xFIP over the next five years.

But no, the Nationals insisted, this had nothing to do with his arm but rather his "mental state", so there goes that article.

By pinning the decision on Strasburg's mental state, the Nationals are short-circuiting any number of arguments with the "You-don't-know-what-we-know" card. It's a good card, with shiny foil edges, a limited-edition number on the back, and maybe a piece of a game-used uniform included. If it were an issue with his arm, you could use incomplete data to make quasi-flawed arguments about whether protecting pitchers actually did anything. But his mental state? How can you, mere mortal, possibly claim to know anything about what Strasburg is thinking or feeling? Or at least, how can you claim to know more than the people in the metaphorical trenches with him?

Friday, September 7, 2012

Bad Beats: Rutgers at Tulane, Sep. 1, 2012

I owe Tulane football an apology. It seems I underestimated this year's team.

When the opening line for the season opener against Rutgers was listed at 17, I immediately jumped on Twitter.
Even when confronted with the one other Tulane football fan on Twitter, I refused to back down.
And it seemed Vegas agreed with me, kind of: by the week of the game, the line had moved to 20, though the over/under still suggested Tulane's score would be a natural number.