THE BOOK--Playing The Percentages In Baseball

Monday, October 31, 2011

RE24/boLI

By Tangotiger, 04:38 PM

As you guys know, I’m big on WPA/LI (aka Situational Wins), even if I can’t articulate it well enough. I’ll get there one of those years.

Similar to WPA/LI (which is the change in win expectancy by game state, divided by the leverage for that game state) is RE24/boLI (which is the change in run expectancy by the 24 base-out states, divided by the leverage for that base-out state).

One set of boLI numbers can be found here. Basically, the highest leverage is with bases loaded, and lowest leverage is with bases empty. You can get a double in either case, but the impact of your double will be felt more with the higher-leveraged state.

So, in order to put both PA on a level playing field, you “deleverage” it by divided the change in run expectancy by the leverage index for that base-out state. Or, so I thought.

I wrote this to Sean Forman (who calculated RE24/boLI on his site) with regards to a Tyler Clippard play:

Sean,

Ok, this is what I’m thinking. Let’s look at this event for Clippard:
game_id event_num inning date_game
ATL201105100 67 8 5/10/2011

There’s runners on first and second, the LI for that base-out state is 1.94. A HR is hit, 3 runs score. The RE delta is -2.38. We would divide that by 1.94 to “neutralize” the leverage.

However, part of that RE delta is the batter himself. He himself is not part of the “extra” leverage. His HR would contribute exactly -1 run to the delta RE regardless of what the boLI is.

So, what really should happen is that you divorce the delta RE between the runners and the batter. The neutralizing of the delta RE should only apply to the runners, not the batter.

I still haven’t thought through it all, but this is where I’m coming from.

I’ll talk to you later.

Tom

So, in the case of my Clippard HR illustration, the -2.38 RE delta was really -1.38 for the runners and -1.00 for the batter. We deleverage the runners by a factor of 1.94 (to get it to -0.71), and we leave the batter untouched (at -1.00), for a total deleveraged RE24 of -1.71.

Compare that to -2.38/1.94= -1.23.

I’m 90% convinced I’m right, but I’d like to hear from the Straight Arrows among you.

(And, if you had questions regarding deleveraging, be it here or with WPA/LI, now’s your chance as well.)

• Sabermetrics • Leverage_Index

#1 Colin Wyers (see all posts) 2011/11/01 (Tue) @ 01:44

The base state may not matter for the odds of the batter-runner scoring, but the outs certainly will.

#2 Tangotiger (see all posts) 2011/11/01 (Tue) @ 09:20

Let’s talk about an easy one: solo HR.

The change in RE is always 1.00 for a solo HR.

The leverage index for the bases empty states is as follows:
0.9 0 outs
0.6 1 out
0.4 2 outs

So here’s the question: when we “deleverage”, do we want the value of the HR to always be 1, or do we want it to be 1.1 runs (0 outs), 1.7 runs (1 out), 2.5 runs (2 outs)?

I’m having a hard time justifying (or rather explaining) what a deleveraged run value of 2.5 means for a solo HR with 2 outs.

#3 James Piette (see all posts) 2011/11/01 (Tue) @ 11:01

Even if you consider RE for a solo HR to be 1, you still need to correct for the negative outcome (i.e. out). However, once you start talking about the value of an out, it is certainly dependent on the situation, so in turn, you must correct for the base-out situation and deleverage accordingly.

...Is that close?

#4 Tangotiger (see all posts) 2011/11/01 (Tue) @ 11:11

Perhaps the better way is to instead of deleveraging, you apply the leverage to the standard weights.

For example, if the standard run value of the HR is 1.40, then with a 0.4 LI, it would be 0.56. Since a HR is worth 1.00 with bases empty 2 outs, then the HR earns +0.44 runs over-and-above its context-neutral value.

So, rather than taking the 1.00 run value of the HR, and dividing that by 0.4 to get us to 2.50 (and compare that to the 1.40), we go the other way instead.

Maybe this makes more sense…

#5 WanderingWinder (see all posts) 2011/11/01 (Tue) @ 15:03

I’m a little confused as to how a ‘properly leveraged’ RE24/boLI is going to be different from linear weights…

#6 Tangotiger (see all posts) 2011/11/01 (Tue) @ 15:12

The basic idea behind RE24/boLI is to put everyone on the same opportunity scale. If you come up with a disproportionate number of bases empty situations (i.e., leadoff hitter), your overall boLI is going to be under 1. If you come up with a disproportionate number of bases loaded or other high leverage base-out situations, your overall boLI is going to be above 1.

So, both guys can have 600 PA, but one guy might have a boLI of 0.9, and so, would only have the impact of 540 PA, and another guy can have a boLI of 1.1, and so have an impact of 660 PA.

Therefore, we’re trying to “deleverage” the base-out leverage in such a way that 600 PA is 600 PA for either of the two players.

A guy who is overall +60 runs in 600 PA will be +54 in one situation and +66 in the other situation, strictly because of the leverage.

We’re trying to untangle the leverage from the performance so that the two, combined, gives us the impact.

That’s where I am right now.

#7 (see all posts) 2011/11/02 (Wed) @ 10:36

I understand that that’s what RE24/boLI is for when you’re looking at it coming from RE24. You think ‘hey, RE24 is a great stat, but different people have different opportunities, lets fix that.’ Fine. Good. What I don’t understand is, isn’t the linear weights ‘HR is 1.4 runs, triple is worth 1.1, etc.’ exactly what you’re looking for there? I mean, isn’t that what those values are, averaged run values of each of those events? And isn’t that what you’re looking for when you want to de-leverage?

On a side note, I really wish I could find where I set my copy of The Book, so I wouldn’t have to rely on my memory here.

#8 Tangotiger (see all posts) 2011/11/02 (Wed) @ 11:09

Those run values are averaged across all base-out states.

Take for example a strikeout with a runner on 3B only, and 1 out. The Leverage Index for that base-out state is 1.1 (basically, average leverage).

But the run values of each event in that base-out state are far different than we are used to.

A regular out is -0.25 runs, but a K is -0.60 runs, much different from the standard -0.28 / -0.29.

A walk is +0.25 runs, while a single is +0.55 runs, fairly different from the +0.32/+0.47.

In this particular case, there’s nothing to “deleverage” because the LI for this base-out state is close to 1.00. What happens is that there’s a “redistribution” of impact. With a runner on 3B, the K is a killer, while a walk has limited value.

So, the delta-RE for the runner on 3B and 1 out represents a fair opportunity (the run impact is neither magnified nor depressed based on the leverage of the base-out situation).

This is not what we find with bases empty (depressed leverage) or bases loaded (magnified leverage). In those cases, one PA counts as 0.4 PA if it’s bases empty 2 outs, or 2.5 PA if the bases are loaded.

So, it’s not “fair” in terms of trying to make each PA have the same impact.

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Monday, October 31, 2011

RE24/boLI

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