JoeDog::Stats (tarball - zip) was updated to version 1.15. This version adds support for the geometric mean in arrays and hash tables.
The Geometric Mean of a set of n positive numbers is the nth root of the product of n numbers. There are two main uses of the Geometric Mean: (1) to average indexes or (2) determine the average percent increase of a series of numbers from one time to another. JoeDog::Stats performs the first function. If you require the latter, let us know.
The Geometric Mean is calculated as follows:
________________ GM = \n/ (x1)(x2)...(xn)
NOTE: if one of the numbers is zero or negative the Geometric Mean cannot be computed. JoeDog::Stats will return "undef" in those cases.
To illustrate the geometric mean consider the following example. If Joe's Bar and Whorehouse made annual profits of 3, 2, 4 and 6% over a period of four years, what is the geometric mean profit?
__________ GM = \4/(3)(2)(4)(6) ______ = \4/ 144 = 3.46
This is slightly less than the artimetic mean which is 3.75. In the example above, Joe had a disproportionately good fourth year that skews his average. The Geometric Mean, therefore, provides a better description of a typical year's profits. The Geometric mean is not as weighted by extreme measures. Because of this, it provides a better indicator or typical experience. It is a good stat to describe positively skewed data such as network performance measures.
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