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Standard Deviation

Posted By: Timothy Chow
Date: Friday, 31 August 2012, at 10:32 p.m.

In Response To: Standard Deviation (Bill Phipps)

Just to point out what should be obvious, but may not be obvious to everyone:

If you want to estimate the probability that, for example, Stick plays higher than 2.64 online, it makes no sense to try to estimate the standard deviation using some assumption about what the distribution is, and then convert back from standard deviation to probabilities. The answer is already staring you in the face, without any calculations: the probability is 25%. That's what "upper quartile" means.

(O.K., an expert will object that the sample upper quartile isn't the same as the actual upper quartile. However, it's still true that converting to standard deviation and back is a poor way to go about this calculation.)

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