Can someone link me to a good explanation of standard deviation. I am not too bad at math but I simply never covered this and I need it. I assume it also has something to do with ln.

All hail Google.
Standard deviation is a statistics measurement that measure how ''spread out'' a distribution is, for lack of a better term.

Explanation:
http://www.robertniles.com/stats/stdev.shtml

Formula:
http://www.maths-help.co.uk/Knowldge/Stat/Twostdev/Question.htm



Check out my raytracer at http://simp-raytracer.sourceforge.net. Download it at http://www.sourceforge.net/projects/simp-raytracer.

Thx

Personally I don''t like that explanation of standard deviation. Too often people refer to the normal distribution, since that''s what they were taught in school.

A far simpler explanation of SD is that it is the square root of the average squared distance (the root mean squared (RMS) deviation) between any point in the distribution and the mean of the distribution. It''s a measure of the average distance from any point in the distribution to the mean.

It is completely irrelevant what type of distribution one is looking (parametric or non-parametric), which is why I find it frustrating that people almost always refer to the Normal Distribution when trying to explain standard deviation.

Cheers,

Timkin