May 8, 2012
Rest-of-Season PECOTA Now Available
We are happy to announce that rest-of-season PECOTA projections are now available and will be updated daily going forward.
The methodology is fundamentally the same as it was last year:
We are not rerunning the entire PECOTA process on a daily basis. First off, that would simply be impractical; by the time we got done the next day’s stats would already be waiting for us. Secondly, it would be the wrong tool for the job. Much of the computational horsepower behind PECOTA is spent figuring out how a player will change with age. The effects of age between now and late August are minimal enough to be ignored, and the aging process used to figure a player’s aging between seasons would be very ill-suited to help us capture them anyway.
Instead, we are taking a player’s season-to-date numbers and, in effect, “regressing” them toward the pre-season PECOTA forecast. The weighting is determined by two things: (1) a player’s playing time so far this season and (2) the reliability of a player’s preseason forecast. The more a player plays this season, the more the rest-of-season forecast can move, but at the same time, the forecast for a rookie is more likely to move than that of an established veteran.
We are also doing in-season translation of minor-league stats this season, and those minor-league translations are being incorporated into the rest-of-season projections (albeit with less emphasis than on the major-league stats).
In addition to updating the forecasts with season-to-date stats, we are now baselining the forecasts against the 2012 season to date, so the projections across the board may have moved some as well to reflect the difference between the 2011 offensive environment and the 2012 offensive environment. This will be part of the daily update, so the PFM data will be baselined against current seasonal averages from this point forth.