
Visualizing Bayes’ theorem (2009) - SimplyUseless
https://oscarbonilla.com/2009/05/visualizing-bayes-theorem/
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ttkeil
I'm still quite fond of the Lego example:

[https://www.countbayesie.com/blog/2015/2/18/bayes-theorem-
wi...](https://www.countbayesie.com/blog/2015/2/18/bayes-theorem-with-lego)

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floatrock
The neat thing about the lego example is it uses overlapping grids instead of
overlapping circles.

Overlapping circles are familiar -- everyone made venn diagrams in primary
school.

Problem is it's notoriously subjective to use circles to map to some quantity.
Visualization blogs are rife with examples of people riffing on visualizations
that confuse mapping circle radius vs. circle area to some quantity.

Using a grid (or legos) is nice because it eliminates that area-vs-radius
ambiguity.

~~~
thomasfl
As soon as I've learned bayes theorem myself, I'll go on and teach my 9 year
old daughter.

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leonnn
This seems to me to be the best way to understand Bayes' theorem, with natural
frequencies being the best way to mentally compute with it. E.g. for the
breast cancer example,

\- Imagine there are 1000 women who participate in routine screening

\- 1% → 10 of these have breast cancer

\- 80% → 8 of these will get positive mammograms

\- 990 don't have breast cancer

\- 9.6% ≅ 10% → 99 of the 990 get positive mammograms

So that the probability of having breast cancer, given a positive mammogram,
is ≅ 8/99 ≅ 8%.

There is a bunch of research on natural frequencies being generally the best
way to reason about this sort of thing.

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satyrnein
I attempted a way to visualize that example (with natural frequencies) here:

[https://medium.com/@eshan/why-nobody-understands-
mammograms-...](https://medium.com/@eshan/why-nobody-understands-
mammograms-81b53f9eb769#.v118lzu8u)

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lordnacho
Isn't this the bog standard way to visualize Bayes' theorem?

Still appreciate it though.

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1971genocide
Took a entire module on Bayesian Method in University.

Failed it.

Gave the exam a second time - this time I spent the whole summer studying it -
failed it again :(

At this point I think bayesian methods is one of those things like Monads -
you either understand it or you never will.

Hopefully there is someone out there who finally writes a good book to explain
it to the masses of simpler minds.

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Xcelerate
> At this point I think bayesian methods is one of those things like Monads -
> you either understand it or you never will.

Add organic chemistry to that list. I can write a program from scratch that
will accurately simulate how two organic molecules react using density
functional theory, but I'll be darned if I ever understand those little
diagrams and arrows.

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foobarbecue
“people with cancer” (designated as A), and “people with no cancer” (or A)

Presumably the second "A" is supposed to appear as some symbol for "not A"? On
my screen it just appears to say A.

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p1esk
Bayes Theorem is easy. But determining its components can get tricky.

