holman/hopper — pull request #13 by KarlHerler (2012-06-20 11:48:49+00:00)
Title: Support standard deviation in the statistical metrics gathered

Because it's a good metric, heck it's a nessesary metric.

In case you've forgotten some of stats 101:
- [Variance](http://en.wikipedia.org/wiki/Variance) shows how spread the numbers are, hence the name. It is basically computed as the average distance from the mean.
- [Standard deviation](http://en.wikipedia.org/wiki/Standard_deviation#Basic_examples) is basically each distance from the mean, like with the variance, only squared (so as to avoid having negative numbers) then averaged and square rooted.

I changed the [app/models/probe.rb](https://github.com/KarlHerler/hopper/blob/patch-1/app/models/probe.rb) to support add support for standard deviations, not sure if it's the right spot but seemed the best (although the documentation only mentioned averages so I changed that).
I havent tested it to be honest, the method exists in [rstats](http://rubydoc.info/gems/rstats/0.0.4/Array:squares_of_deviations) so it should be peachy-fine but nevertheless **you've been warned**.