CSS Button No Image Css3Menu.com

Baseball Prospectus home
  
  
Click here to log in Click here for forgotten password Click here to subscribe

Premium and Super Premium Subscribers Get a 20% Discount at MLB.tv!

<< Previous Article
Premium Article Prospects Will Break Y... (01/06)
<< Previous Column
BP Unfiltered: Rereadi... (01/02)
Next Column >>
BP Unfiltered: Rereadi... (01/09)
Next Article >>
Premium Article Minor League Update: I... (01/07)

January 7, 2014

BP Unfiltered

Rereading Nate Silver: 15. Updated PECOTAs

by Sam Miller


In which Nate provides a simpleish way of updating your expectations.

Binomial Distribution (or What the Heck is Up with Miguel Tejada and Alex Gonzalez?)
May 7, 2003

Abstract: A month into the season, Nate tries to fashion a sort of PECOTA update using binomial distributions. Basic premise: If PECOTA thinks Miguel Tejada is a .270 hitter, but he’s hitting .370, and binomial distribution estimates a very low likelihood that a .270 hitter could hit .370 over a month, then it’s very unlikely that Tejada is a .270 hitter, after all. If I correctly understand what he was doing, he basically charted two probability lines, like this,

and where the two lines met he declared a new truth existed.

Key quote: “Ichiro has the capacity to change his approach, but seems uninterested in doing so; as he continues to age, his slap-hitting ways will seem ever more gradually out of place, until one day he's Larry Eustachy at a sorority party.”

Results: Nate gave 12 “corrected” projections. Imagine that all 12 players were projected to hit .270, but the new projections said they’d hit .280, and all 12 had hit below .270. We’d fairly conclude that the binomial distribution patch was overestimating players’ new developments. If they all hit over .280, we’d conclude that PECOTA was overweighting the past, or was overweighted in Nate’s new math. In fact, though: According to Clay Davenport’s historical EqAs, six of the projected hitters hit the under*, five hit the over, and one was spot on the new projection. The thing worked!

If you’re smart, you can probably use this, somehow.

*under, in this case, means the final result was closer to the previous projection than the new projection was. Because Nate looked at players who had hot starts and players who had cold starts, “under” might mean that the batter hitter better than his projections. Under=over, sometimes. Make sense?

Tables: 0
Graphs: 2
Equations: 0
Broken Links/Total Links: 3/5

On the Nate Silver Must-Read Scale: 1

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

0 comments have been left for this article.

<< Previous Article
Premium Article Prospects Will Break Y... (01/06)
<< Previous Column
BP Unfiltered: Rereadi... (01/02)
Next Column >>
BP Unfiltered: Rereadi... (01/09)
Next Article >>
Premium Article Minor League Update: I... (01/07)

RECENTLY AT BASEBALL PROSPECTUS
Fantasy Article Fantasy Starting Pitcher Planner: Week 19
Barbecue State of Mind
Premium Article Transaction Analysis: Give the Red Sox Your ...
Premium Article Transaction Analysis: Astros, Marlins, Swap ...
Premium Article Transaction Analysis: The Great Big David Pr...
Premium Article The Call-Up: Mike Foltynewicz
Trade Deadline

MORE FROM JANUARY 7, 2014
Premium Article Skewed Left: What the 1936 Hall of Fame Ball...
Premium Article Perfect Game Presents: Before They Were Pros...
Baseball ProGUESTus: The 2013 All-Out-of-Pos...
Premium Article Rumor Roundup: Which Teams Are in on Tanaka?
Premium Article Hot Stove Scouting Report: James Loney
Premium Article Minor League Update: International Winter Le...

MORE BY SAM MILLER
2014-01-09 - BP Unfiltered: Rereading Nate Silver: 16. Ba...
2014-01-08 - BP Daily Podcast: Effectively Wild Episode 3...
2014-01-07 - BP Daily Podcast: Effectively Wild Episode 3...
2014-01-07 - BP Unfiltered: Rereading Nate Silver: 15. Up...
2014-01-06 - BP Daily Podcast: Effectively Wild Episode 3...
2014-01-03 - Premium Article Pebble Hunting: The Weirdness of Walking Bar...
2014-01-03 - BP Daily Podcast: Effectively Wild Episode 3...
More...

MORE BP UNFILTERED
2014-01-10 - BP Unfiltered: Rereading Nate Silver: 17. Th...
2014-01-09 - BP Unfiltered: YCPB and You Never Could
2014-01-09 - BP Unfiltered: Rereading Nate Silver: 16. Ba...
2014-01-07 - BP Unfiltered: Rereading Nate Silver: 15. Up...
2014-01-02 - BP Unfiltered: Rereading Nate Silver: 14. Sa...
2013-12-31 - BP Unfiltered: One Last GIF For 2013
2013-12-24 - BP Unfiltered: Forgot About Dre Lyrics Repla...
More...