THE BOOK--Playing The Percentages In Baseball

Friday, April 18, 2008

Not EXACTLY one run, but AT LEAST one run

By Tangotiger, 08:50 AM

Smart people make this mistake all the time, but friend-of-The-Book Joe Sheehan doesn’t:

...with a runner on second and no one out, you have a 62.5% chance of scoring one run. With a runner on third and no one out, you have an 82.7% chance of scoring one run. With one out and no one on, you have a 16.5% chance of scoring one run

He references BBTN, and we have it in The Book as well, but, I’ve also got it online right here. While he did say “one run”, he really meant “at least one run” and not “exactly one run”. And his numbers bear that out. And he was right to compute it that way. With one out and no one on, the chance of scoring exactly one run is 10%. But, the chance of not scoring at all is 83%, meaning the chance of scoring at least one run is 17%. And that is the number we care about. Invariably, we almost always want to know chance of scoring not at all, or its complement. (His 82.7% for runner on 3B looks mighty low. I have it at 86.4 for 1999-2002. Did he mean to say 87.2%?)

Good job to Joe in not falling into the trap. Admiral Ackbar has snagged many a fine folk.

• Sabermetrics • Run_Win_Expectancy

#1 MGL (see all posts) 2008/04/18 (Fri) @ 18:28

It would have been nice had Joe said “at least one run,” since the words “one run” means “exactly one run.” It certainly doesn’t mean “at least one run.” He is perpetuating the mistake. So I’ll give Joe half credit!

#2 SirKodiak (see all posts) 2008/04/18 (Fri) @ 19:37

One study I would love to see is a comparison between the run scoring environment with:

1. a team that focused on scoring one run every inning (and once you score one run, focus on a second, etc); and

2. a team that focused on maximizing RE each and every inning.

#3 SirKodiak (see all posts) 2008/04/19 (Sat) @ 03:55

The context of the article was tied, in extra innings, with the home team at bat, so one run was all that mattered and he probably had that on his mind.

#4 MGL (see all posts) 2008/04/19 (Sat) @ 14:00

And no one could hit a multi-run homer?

#5 tangotiger (see all posts) 2008/04/19 (Sat) @ 16:14

I don’t think that’s what he had on his mind. As I said, he presented the correct numbers, those of 1+ runs. Therefore, he knew what he was talking about. The words he used are ambiguous, but his numbers are not.

#6 MGL (see all posts) 2008/04/20 (Sun) @ 21:42

Tango, I agree that the numbers are correct and he obviously knows what he meant and what is correct. I am saying that the words were NOT ambiguous. “The chances of scoring 1 run” means only one thing, in common English usage at least. We know what some people mean when they say that, but that has nothing to do with language. There is NO ambiguity in that sentence or statement. None, whatsoever. As I said, I give Joe only half credit, because one of the reasons for the “confusion” over the years is that people often use the wrong words. If I am figuring the chances of doing “at least anything” that is exactly what I say. If I am figuring the chances of doing EXACTLY something, then I either say “exactly” or I leave out that word completely. Either way, the meaning is EXACTLY the same. Joe did the right calculations, but clearly used the wrong words, which is OK. I screw up my words all the time.

#7 MGL (see all posts) 2008/04/20 (Sun) @ 21:44

OK, I’ll back up a little. “The chances of scoring one run,” is a little ambiguous, since I guess when you score more than one run, you also score one run. Nonetheless, Joe should have used the correct words, especially since that is an area that people mess up all the time.

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