Here is the link to the explaination of PECOTA from BP's website.
Here is an idea of how it works. For a full desrciption go to the site.
baseball prospectus glossary wrote:Comparable Players are the backbone of a player's PECOTA. Only the twenty best comparables are listed here, but as many as 100 players may be used in the generation of his forecast if they are sufficiently comparable.
PECOTA compares each hitter against a database of roughly 20,000 major league batter seasons since World War II. In addition, it also draws upon a database of roughly 10,000 translated minor league seasons (1998-2005) for hitters who spent most of their previous season in the minor leagues. (When minor league comparables are used, they appear in ALL CAPS). PECOTA considers four broad categories of attributes in determining a hitter's comparability:
1. Production metrics--in particular, batting average, isolated power, unintentional walk rate, strikeout rate, groundball:flyball ratio and a modified version of the Bill James speed score.
2. Usage metrics, including career length and plate appearances.
3. Phenotypic attributes, including handedness, height and weight.
4. Fielding Position. PECOTA doesn't require that a comparable hitter play the same defensive position; it is a factor that is evaluated along with many others, and assigned a relatively substantial weight. Consideration is also given to the 'similarity' between two positions; for example, a shortstop will be compared to a second baseman before he is compared to a left fielder. (See additional discussion).
PECOTA compares each pitcher against a database of roughly 15,000 major league pitcher seasons since World War II, and 10,000 minor league pitcher seasons from 1998-2005. Pitchers are compared only against others of the same age. PECOTA considers three broad categories of attributes in determining comparability:
1. Production metrics such as strikeout rates, walk rates, isolated power and batting average against, and groundball:flyball ratio.
2. Usage metrics such as career length, total batters faced, and percentage of innings pitched in starting/relief.
3. Phenotypic attributes, including handedness, height, and weight.
In most cases, the database is large enough to provide a meaningfully large set of appropriate comparables. When it isn't, the program is designed to 'cheat' by expanding its tolerance for dissimilar players until a reasonable sample size is reached. In the case of very old or very young players, there may not be a significant number of pitchers who appeared in the major leagues at all at that age, and so the results of their forecast may be unreliable.
Halos17, I'm with you. I was planning on going with Baseball Notebook's projections until David Luciani decided to quit, which kind of soured me on the whole thing.
So now I'm looking into using PECOTA, but I feel like Baseball Prospectus doesn't have anything that instructs you on how to use their projections. The glossary is interesting, but there doesn't seem to be an overview with tips on how to apply them.
Does anyone have suggestions on how to go about putting PECOTA to use? Also, does BP generate a ranking list based on your league parameters, as Baseball Notebook does?
No clue re the specific questions but I was reading the 2005 BP book for fun tonight and was kind of alarmed at it being kind of off on a number of young studs, eg. Howard, Wright, Herida, etc. I can totally understand where the numbers and size of their database would squoosh young hitters but, at the same time, it makes me wonder how much value it really has and if it might sort of end up being just another 'if you throw a pot of spaghetti at the wall X% of it will stick' kind of thing. I like Forecaster better but have not gotten to the point where I've wanted to spring for either website.
It was kind of amusing reading about how the White Sox and Astros were going nowhere though...
I'm not sure what you guys are talking about. Firstly you have to be a subscriber to have access to the PECOTA projections. Secondly, they project all of the 5x5 categories, so they are effectively predicting what they will do. And as thedude mentioned, Ryan Howard is pegged to hit 41 HR's so I hardly see how it is holding down young players.....
1) Do the books provide any different info than the website, or is it just a matter of convenience?
2) Do subscribers actually have access to the formula they use, or is it a big family secret like the KFC recipe?
1) Not sure, haven't book the book. I think it gives you more in depth analysis of players individually and maybe even prospects.
2) It's not as simple as a formula where you input the players past statistics. It draws upon databases of thousands of players and finds comparable players, and what career paths they followed. I think it also adjusts for alot of other factors to: playing time, lineup, home ballpark etc.
I can answer the book part, it's got a scouting report format, going team by team through the league w/ a writeup and projections for each player, including stats going back a few years. The writeups are very entertaining stuff. There's an introductory 'how to use this book' section, a section on minor leaguers and then some articles which are sort of like appendices at the end.
The Pecota numbers for each player, are based on analysis of historical trends in baseball, are expressed as %ages that the player will Breakout, Improve, or Collapse. Which is fairly simple and has some appeal but looking at it w/ hindsight, I'm not sure if it was that much more amazing than any other type of projection/ guess. It is good reading though and has a lot of interesting stuff about what directions teams are moving in.
I'd suspect that the Website info is a lot more up to date as draft day approaches. While I haven't subscribed, I do check out their freebies. I just am averse to paying for crap on the internet but have no problem buying books. I may be dating myself...