úterý 14. února 2012

O slepotě vůči černým labutím

Taleb chce ve své knize ukázat, že vinou svých vědátorských teorií slepneme před nepravděpodobnými událostmi, které ovšem nadmíru pravděpodobně přijdou, a že praktičtí lidé se zdravým rozumem jsou tudíž mnohem hodnotnější než školometi. Ale říká to dosti divně.

NNT (that is, me): Assume that a coin is fair, i.e., has an equal probability of coming up heads or tails when flipped. I flip it nineny-nine times and get heads each time. What are the odds of my getting tails on my next throw?
Dr. John: Trivial question. One half, of course, since you are assuming 50 percent odds for each and independence between draws.
NNT:  What do you say Fat Tony?
Fat Tony:  I'd say no more than one percent, of course.
NNT: Why so?  I gave you the initial assumption of a fair coin, meaning that it was 50 percent either way.
Fat Tony:  You are either full of crap or a pure sucker to buy that "50 pehcent" business. The coin gotta be loaded. It can't be a fair game. (Translation: It is far more likely that your assumptions about the fairness are wrong than the coin delivering ninety-nine heads in ninety-nine throws.)
NNT: But Dr. John said 50 percent.
Fat Tony (whispering in my ear):  I know these guys with the nerd examples from my bank days. They think way too slow. And they are too commoditized. You can take them for a ride.
Nassim Nicholas Taleb - The Black Swan: The Impact of the Highly Improbable

Kdo zde neuznává, že nepravděpodobná událost může nastat, a kdo to připouští? Ale třeba Tomáš Sedláček označuje Černou labuť za pronikavou a hlubokou knihu. Jen nevím proč. Neumím říct, jestli Sedláčkova kniha Ekonomie dobra a zla by šla sama o sobě označit za pronikavou a hlubokou. Ve srovnání s Talebem však rozhodně ano. Mimochodem, něco podobného jako citovaná ukázka můžeme najít i u Pratchetta. Je dokonce možné, že je to i relevantnější:

"Well," said Ponder, gratified at the attention, "it appears that there was this man, right, who had to choose between going through two doors, apparently, and the guard on one door always told the truth and the guard on the other door always told a lie, and the thing was, behind one door was certain death, and behind the other door was freedom, and he didn't know which guard was which, and he could only ask them one question and so: what did he ask?"
The coach bounced over a pothole. The Librarian turned over in his sleep.
"Sounds like Psychotic Lord Hargon of Quirm to me," said Ridcully, after a while.
"That's right," said Casanunda. "He was a devil for jokes like that. How many students can you get in an Iron Maiden, that kind of thing."
"So this was at his place, then, was it?" said Ridcully.
"What? I don't know," said Ponder.
"Why not? You seem to know all about it."
"I don't think it was anywhere. It's a puzzle."
"Hang on," said Casanunda, "I think I've worked it out. One question, right?"
"Yes," said Ponder, relieved.
"And he can ask either guard?"
"Oh, right. Well, in that case he goes up to the smallest guard and says, Tell me which is the door to freedom if you don't want to see the colour of your kidneys and incidentally I'm walking through it behind you, so if you're trying for the Mr. Clever Award just remember who's going through it first.'"
"No, no, no!"
"Sounds logical to me," said Ridcully "Very good thinking."
Terry Pratchett - Lords and Ladies

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