Auc-Stat-StdDev

From Norganna's AddOns

Purpose

This module is an example of a statistics module that allows elimination of outliers by using the Standard Deviation algorithm to find the standard deviation from the mean. From this point a new mean (normalized mean) is created using only those data points that are within 1.5 standard deviations of the actual mean.

Strengths

This algorithm is quite good at working out a reasonable price for your item, and discarding the outliers.

Weaknesses

Only the last 100 data points are kept, so if it's an item that is seen quite frequently on your server, this can recycle rather quickly.

Technical

There is a good wikipedia page on Standard Deviation that may help fill in any blanks.

Basically, if you're a coder and want some pseudo code:

foreach prices do
  variance += abs(mean - price)
end
variance = variance / count(prices)
stddev = squareroot(variance)
foreach prices do
  if abs(mean - price) < (stddev*1.5) then
    normal += price
    normalcount++
  end
end
normal = normal / normalcount