MLB over-unders: Can anyone beat Las Vegas?
Back in March, several dozen websites, written by either professionals, bloggers, or, in some cases, professional bloggers, came out with predicted MLB win totals.
A predicted win total represents the number of wins this website or individual predicted for each major league team. These numbers can be easily compared to the Las Vegas line for each team (I used the one set by the Hilton) to determine if these predictions are worth our time, and, in some cases, our money.
Here are the sites I used:
O/U: The Hilton’s over/under for each team
BP: Baseball prospectus
TR: Team Rankings (caveat on the linked page: the site stresses their MLB predictions are a work in progress)
Zips: ZIPS projection system (espn.com)
PM: Prediction Machine
TB: Trading Bases, an avid blogger and book-writer
Here are my metrics
MSE: Averaged squared error between the prediction and the win totals*
MAE: Averaged absolute error between the prediction and the win totals*
Corr: Correlation between the predicted and the win totals*
*For win totals, I’m use each team’s estimated win totals from here (I’m too excited to wait until the end of the season!)
Baseball prospectus appears to offer the only clear advantage over the Las Vegas line, at least among these predictions, as judged by a higher correlation and a lower MSE between observed and predicted values. As for team rankings & prediction machine, their results were both disappointingly bad. (Note: Trading Bases came into the picture after the initial post, and also appears to be a clear winner).
TeamRankings does offer this disclaimer about their projections:
A word of caution — while our preseason projections for other sports have proven to be useful indicators of where values may lie among the various full season futures bets, we’re not nearly as confident in our MLB preseason ratings. We’re publishing these in the interest of full disclosure, so that you know what the initial rating in our projection system was for each team. We’re most definitely not recommending that you use these ratings and forecasts to go place preseason bets.
Here’s the table of predicted wins for each site.