Lumifer comments on How valuable is it to learn math deeply? - Less Wrong

20 Post author: JonahSinick 02 September 2013 06:01PM

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Comment author: Lumifer 11 October 2013 04:19:46PM 0 points [-]

the true distribution is a mixture of Gaussians

In the limit, the mixture of Gaussians is a Gaussian.

It's not clear to me that malnourishment leads to multiple modes, rather than just decreasing the mean while probably increasing the variance

Theoretically, malnourishment (given that only a part of the population suffers from it) should lead to a negatively skewed distribution. And yes, with a lower mean and higher variance.

Comment author: Vaniver 12 October 2013 03:19:25AM 3 points [-]

In the limit, the mixture of Gaussians is a Gaussian.

Nope. The sum of Gaussian random variables is a Gaussian random variable, but a mixture Gaussian model is a very different thing. (In particular, mixture Gaussians are useful for modeling because their components are easy to deal with, but if you have infinite mixtures you can faithfully represent an arbitrary distribution.)

Theoretically, malnourishment (given that only a part of the population suffers from it) should lead to a negatively skewed distribution.

Yep, I should have mentioned that also.

Comment author: Lumifer 15 October 2013 07:11:20PM 3 points [-]

Yes, you are correct, I got confused between a sum and a mixture.