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July 19, 2011

BP Unfiltered

PECOTA, Pitcher WARP, and PADE Updates

by Ben Lindbergh

Thanks to the hard work of our statistical and technical teams, our signature BP stats have gotten an overhaul this season, both on the surface and under the hood. As often tends to be the case with ambitious projects, we've had a few hiccups along the way, some of them more noticeable than others, and none of them the kind you can cure by holding your breath and chugging a glass of water (not that we didn't try that, just in case). We've been reexamining old ideas and assumptions, and that's why you've seen some values change or fluctuate. In the process, we've also made a few regrettable missteps. Fortunately, we've managed to resolve the most serious issues, so it's time for an update on where some of our statistical offerings stand:

  • Pitcher WARP: As a number of you noticed,  Derek Lowe's WARP looked oddly high for a pitcher with his unspectacular peripherals. We've examined our code and uncovered a bug for which Lowe was the poster boy, if not the lone pitcher affected. The bug resulted in an incorrect boost in FAIR_IP for extreme groundball pitchers like Lowe, which in turn produced bumps in VORP and WARP, counting stats that are based on FAIR_IP. As soon as this fix was implemented, Lowe's PWARP dropped from 4.0 to 2.4, which is likely to be regarded as an uncontroversial change by everyone other than Lowe.
  • Rest-of-season PECOTA: We've made changes to the weighting of recent results that reduced the impact of 2009-2010 performance on players' rest-of-season projections, making them less susceptible to being swayed by small-sample stats. Those changes are now reflected in the "2011 Projections" table at the top of each player card, as well as in our Playoff Odds.
  • PADE: Park-Adjusted Defensive Efficiency is now fully operational. The Rays are doing so well in the PADE department, you'd think a member of their front office might've invented it.
In our 15 years of existence, BP has created a number of new ways of looking at the game from a statistical point of view. Some have stood the test of time, while others have been superseded by new research. In our ongoing effort to hack through the statistical thicket and boil our offerings down to the essentials, our goal is to create clarity where there is now a tangle of overlapping and sometimes contradictory statistics offered not only by us, but by our respected colleagues and competitors.
In every case, it is our goal to present you with all the information necessary to construct the most accurate picture of baseball as it is played today. In the coming weeks, you will see us continue to add statistics and sharpen others. We regret any errors, an inevitable consequence of experimentation, and we welcome further feedback.

Ben Lindbergh is an author of Baseball Prospectus. 
Click here to see Ben's other articles. You can contact Ben by clicking here

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<< Previous Article
Premium Article Future Shock: Monday-M... (07/18)
<< Previous Column
BP Unfiltered: Jim Joh... (07/19)
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BP Unfiltered: Get a J... (07/22)
Next Article >>
Fantasy Article Fantasy Beat: Kimbrel ... (07/19)

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