
Bayes' Theorem explained by Yudkowsky - spydez
http://yudkowsky.net/rational/bayes
======
aswanson
Went back and re-read his tribute to his brother/exhortation to move forward
science again. It's like _You and Your Research_ on steroids. If that essay
doesn't motivate you, I don't know what will. Insanely brave.

~~~
yters
Has someone figured out a way around the 2nd law of thermodynamics? Or is it
not a law anymore? I'm not a physicist, so I don't know these things.

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rms
<http://www.multivax.com/last_question.html>

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yters
That's a sci fi story, not hard science.

Absolutely nothing integral to the singularitrons' vision has been
demonstrated to any extent. Instead, the opposite is shown by the fact cpu
speeds have leveled out.

~~~
aswanson
<http://en.wikipedia.org/wiki/Maxwell%27s_demon>

<http://news.ycombinator.com/item?id=110074>

~~~
yters
Thanks, those are interesting links. Still, nothing there that seems
especially compelling.

Maxwell's demon assumes the energy cost for sorting the molecules is less than
the net gain. That looks like another variant of the perpetual motion machine.

The fluctuation theorem says the 2nd law doesn't hold for very, very small
entities, but its probability of being correct climbs exponentially as the
system scales. So, it is fallacious to then say the 2nd law may not hold at
the macro level due to it not holding at the micro level, since the theorem
used to support this idea is itself an instance of the idea being false.

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Retric
It's always surprising that most people are that bad at math.

.01 x .8 /(.01 x .8 + (.99 x 9.6 / 100)) ~= 0.0776 or 7.8%

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tl
Sure, but we expect doctors (who receive much greater education and
compensation than most people) to get it right.

~~~
dhbradshaw
What's alarming and interesting isn't that they have a lot of years of school
and miss this, but that interpreting diagnostic tests correctly is a core part
of their job and they miss it. How many lives are adversely effected and how
many billions are wasted by doctors making inappropriate decisions because
they don't know how to interpret data correctly?

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Retric
A few years ago I read that around 50% of all medicine prescribed in the US is
providing zero or less net benefit to the patient. Granted by prescribing
something doctors get you out of the office and in a few days most things get
better on their own. But a lot was simple misunderstanding on the part of
doctors about how helpful a given drug actually was.

~~~
michaelkeenan
In case you want to find your source, I'm guessing it was economist Robin
Hanson:

[http://www.cato-unbound.org/2007/09/10/robin-hanson/cut-
medi...](http://www.cato-unbound.org/2007/09/10/robin-hanson/cut-medicine-in-
half/)

~~~
Retric
No, it was specifically talking about prescribed medicine. Granted not the
cost of said medicine. Something like this
(<http://www.nytimes.com/2008/10/24/health/24placebo.html>) but rather
reviewing what drugs patents where taking and comparing it to their symptoms.

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rms
This is my favorite writing by Yudkowsky:
<http://www.overcomingbias.com/2008/05/faster-than-ein.html>

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jcl
It bugs me a little that he starts using the phrase "prior probability" before
defining it. If your vocabulary already included the word "priors", you
probably wouldn't need a Bayes tutorial. :)

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herdrick
[java applet] [java applet] [java applet] [java applet] [java applet]

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herdrick
Which is not to say you shouldn't click! In fact these are the most useful
Java applets I've ever seen. He still should've done them with Flash, though.

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kirse
Do significant digits matter in these sort of probability calculations?

Secondly, do we want doctors to tell us the probablility estimate that we have
cancer or do we want doctors to tell us Yes or No?

Personally, I don't care what my probability score is if the answer is "No".
Even if the answer was "Yes", an optimistic person would ignore the odds
anyway.

~~~
gjm11
Yes, I want the probability estimate, because I want the best information
available in that sort of situation. And the word for someone who ignores the
odds is not "optimistic" but "foolish", unless the answer makes no difference
to your behaviour. (Which is pretty unlikely in the case of cancer.)

