Why does WoWuction choose Median over Average?

[Stalkr]

Hello Goblins,

so today I fiddled around with the Auc-Stat-Wowuction module for Auctioneer,
an AddOn I can't live without. Also got myself the TSM application so I am always up to date.

However, I came across a scenario today and I really wondered why it chose median over the market value.
The 'issue' is [Elemental Fire] -



As you can see, the lowest buyout is 1000g which is just crazy as it is only worth 22s.
Auctioneer tries to undercut by using the value of WoWuction times 1.25 (25%) as displayed in the right column (Undercut % change: 25)

What I don't understand is: wouldn't it be better to use the market value, add the 5s and times that with 1.25?
So instead of the median value @ 10s * 1.25, I would think (22s + 5s) * 1.25

Now, I understand that median is the middle item/price of a sorted list and I guess it uses that because it knows 10s + 8s is no way near 1000g.
Then why doesn't it use (10s + 8s) * 1.25 to try and find the highest undercut price, without posting crazy values?
That would be 22s5 or 33s75 instead of only 12s50.

I know this example sounds crazy for only 12s50 - who cares about those small values?
I guess it's the principle behind it, what if it was 1000g median and 1250g market? Now that's a huge difference and would be a lost of 250g. I guess it's best and safest to always manual check auctions at those prices, but trying to keep things as automated as possible, I just don't understand the logic :-)

P.S. I know you may not have anything to do with the Auctioneer module, just hoped that someone could answer the logical reason for this sort of behavior. Thanks for reading.

[wowuctioneer]

Hi!

Auc-Stat-WoWuction is made by @dellantha , who is a member of this forum. So maybe he can give more insight into what's going on.

From the price statistics perspective, Market Value and Median shouldn't be far off for items with stable prices. When you encounter such a big difference it means one of the two things:
a) the price of the item is increasing a lot over the time (since market value tries to predict market trends, while median doesn't)
b) the price for the item is not really stable and fluctuates erratically

I'd say that in your case it's the (b) option. When you encounter something like this you should always use your common sense in pricing and maybe check additional data on the www.wowuction.com (for example price history graph).

If the cheapest item is 20s one day and 100g the other, no statistical tools will help you. I personally stay out of such markets, but some super-cunning people can use this as an advantage and sell scarce items for high premium prices.

Hope this helps!

[Skroo]

I usually look at the std dev for an item and use that to judge which value to use. If the median is 500g and the ave is 2,000g with a 1,200 std dev then I go with the median usually ... or median +25%.

This happens in the transmog market all the time since a lot of items might not be seen by the pricing sites on your server for long periods of time.