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THE BOOK--Playing The Percentages In Baseball

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Friday, June 03, 2011

Reader Mail of the Day: What is luck?

My answer:

Michael,

I agree that, 100%, luck is the random occurrence centered around a true mean.  In effect, EVERYTHING in the world is luck, since something either did (1) or did not (0) happen.  There’s no such thing as something “partially” happening.  If someone has a .420 OBP, he won’t get on base 42% of the time in his next PA.  He either is, or is not, on base.  So, whether he got on, or not, is luck.  The FREQUENCY over a long period of time, is not luck.  But, any single event is luck.

That’s the tough part to get through that, any single occurrence is random, but it’s random based on the true mean.  A goalie saves 90% of his shots, so, he’ll get a save (1) far more than a goal (0). But any single event (save or goal) is luck.

To make it worse, the mean is not even constant!  If there’s a breakaway, his chance at a save is 65%, but if he’s got all 5 of his teammates, and only 1 shooter, his chance at a save would be 95%.

Tough concept.

Tom

***

To further add: the “true mean” is based on everything we know, and don’t know, about the environment.  That is, god herself told you the odds of something happening based on the properties of each entity.  When something happens, or not, that’s luck.  It’s the random occurrence (1 or 0), but predicated on the true mean (whatever it is, but it has to be greater than 0 and less than 1).

If one thing has a 100% causal effect to another thing, that has nothing to do with luck, and is instead, fate.  We’re not talking about fate.

And, I’m not talking about things “outside my control”.  That’s not luck.  That’s simply a gap in knowledge.

I’m talking about you know exactly the true odds of something happening.


(69) Comments • 2011/06/08 • SabermetricsStatistical_Theory
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