
What is Bayesianism? - rms
http://lesswrong.com/lw/1to/what_is_bayesianism/
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mumrah
The conditional probability of A given B is my shepherd, I shall not want. It
makes me multiply through marginal probabilities, it leadeth me beside flat
priors...

And the people sang "P of A given B is equal to the prior probability of A
times P of B given A over the marginal probability of B"

~~~
evanrmurphy
P(Amen | That comment) > P(Miracle)

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JeffJenkins
This is a bit more technical, but still somewhat on topix. Andrew Gelman did a
great "criticism" of Bayesian analysis on April Fools 2008:

[http://www.stat.columbia.edu/~cook/movabletype/archives/2008...](http://www.stat.columbia.edu/~cook/movabletype/archives/2008/04/problems_with_b.html)

Followed later by his response to himself with some other statisticians:

[http://www.stat.columbia.edu/~cook/movabletype/archives/2008...](http://www.stat.columbia.edu/~cook/movabletype/archives/2008/07/responses_to_my.html)

~~~
MikeCapone
Here's a BloggingHeadsTV episode where Gelman discusses this (among other
things) with Eliezer Yudkowsky:

[http://lesswrong.com/lw/1bf/bhtv_eliezer_yudkowsky_and_andre...](http://lesswrong.com/lw/1bf/bhtv_eliezer_yudkowsky_and_andrew_gelman/)

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lutorm
The trouble with applying Bayesianism in science is that your conclusion
becomes dependent on what priors you think are reasonable. If different people
disagree about that, then it becomes a debate about beliefs, not science.
(Unless the priors can actually be determined, of course.)

This seems to largely be the case in climate issues, where it's clear that
some people have such strong priors against anthropogenic climate change that
the evidence needed to convince them outstrip what science reasonably can
provide.

~~~
kaj_sotala
Would the climate issue thing be any different even if nobody applied any
Bayesian methods and only went by frequentist statistics?

It's not that this is a problem with applying Bayesianism in science, it's
that our thought is Bayesian on a fundamental level. And it couldn't be
otherwise, at least not for beings as intelligent as humans.

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niels_olson
Here's a simple, applied example I came up with while I was applying to med
school: <http://nielsolson.us/MedSchool/#odds>

[edit]: there was subtraction error, now fixed.

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DanielBMarkham
I listened last year to a great set of lectures about the Philosophy of
Science. Too much to go into here, save for the fact that, at the end of the
day, it very well may end up that probabilities are all we have to go on for a
wide swath of things.

I'm not yet ready to make the leap to total Bayesianism -- those priors can
really bite you when you least expect it -- but there is some really good
stuff here. Thanks Kaj.

Perhaps we'll see some kind of structured cross between Peirce and Bayes in
the next few decades.

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bradbeattie
It's been a while since I've worked with conditional probabilities, but isn't
he missing the case in which the headache is caused by both a cold and a
tumor?

~~~
lutorm
Yeah, but since that probability of that happening is the product of the two
probabilities, it's probably not a big deal. If the two probabilities were
each 75%, then you'd be in trouble.

