PECOTA

From Wikipedia, the free encyclopedia

You have new messages (last change).

PECOTA, an acronym for Player Empirical Comparison and Optimization Test Algorithm, is a sabermetric system for predicting Major League Baseball player performance.[1] It was invented by Nate Silver of Baseball Prospectus. It relies on fitting a given player's past performance statistics to the performance of "comparable" Major League ballplayers by means of similarity scores. Separate sets of predictions are developed for hitters and pitchers. The comparable players are drawn from a statistical database of all Major League player-seasons since 1946. The raw statistics in this database are first adjusted to take into account the ballparks a player played in (park effects) and the era in which a player played, in order to make them equivalent over time.

Unlike performance forecasts that commonly assume a single pattern of change during a player's career, PECOTA employs several models that take into account not just a player's performance in the previous three years but also his age, speed, handedness, and body type (basically, body mass index). Furthermore, instead of focusing on making point estimates of a player's future performance (such as batting average, home runs, and strike-outs), PECOTA relies on the historical performance of the given player's historical "comparables" to produce a probability distribution of the given player's predicted performance during the next five years.

First introduced in 2003, PECOTA projections are produced each year and published both in the Baseball Prospectus annual monographs and on the BaseballProspectus.com website.[2] PECOTA has undergone several improvements since 2003. The 2006 version introduced metrics for the market valuation of players based on the predicted performance levels. The logic and methodology underlying PECOTA have been described in several publications (see References), but the detailed formulas are proprietary and have not been shared with the baseball research community. The test of PECOTA is its ability to make accurate forecasts in comparison with alternative forecasting methods.

Although designed primarily for predicting individual player performance, PECOTA has been applied also to predicting team performance. For example, PECOTA has been used in preseason forecasts of how many wins teams will attain and in mid-season simulations of the number of wins each team will attain and its odds of reaching the playoffs.[2] In 2006, PECOTA's preseason forecasts compared favorably to other forecasting systems (including Las Vegas betting line odds) in predicting the total number of wins teams would have.[3]

[edit] Citations

  1. ^ The acronym was actually based on the name of journeyman major league player Bill Pecota,[1] who with a lifetime batting average of .249 is perhaps representative of the typical PECOTA entry.
  2. ^ Baseball Prospectus Statistics: http://www.baseballprospectus.com/statistics/ps_oddspec.php
  3. ^ Nate Silver, "Projection Reflection," BaseballProspectus.com, October 11, 2006 http://www.baseballprospectus.com/article.php?articleid=5609.

[edit] References

Alan Schwarz, "Predicting Futures in Baseball, and the Downside of Damon," New York Times, November 13, 2005.

Nate Silver, "The Science of Forecasting," BaseballProspectus.com, March 11, 2004, available at http://www.baseballprospectus.com/article.php?articleid=2659.

Nate Silver, "Introducing PECOTA," Baseball Prospectus 2003 (Dulles, VA: Brassey's Publishers, 2003): 507-514.

Nate Silver, "PECOTA Takes on the Field: How'd It Fare Against Six Other Projections Systems?" BaseballProspectus.com, January 16, 2004, available at http://baseballprospectus.com/article.php?articleid=2515.

Nate Silver, "PECOTA 2004: A Look Back and a Look Ahead," Baseball Prospectus 2004 (New York: Workman Publishers, 2004): 5-10.

Nate Silver, "Rearranging PECOTA," Baseball Prospectus 2006 (New York: Workman Publishers, 2006): 6-11.

Retrieved from "http://en.wikipedia.org../../../p/e/c/PECOTA_3057.html"