  
| Author: | jeslego  | | Posted: | Jul 20, 2016 10:07 | | Subject: | Re: standard deviation on price indices | | Viewed: | 32 times | | Topic: | Suggestions | |
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| In Suggestions, FigBits writes:
| | In Suggestions, brick_projects writes:
| | Please implement standard deviation.
By eliminating the (small number)% cheapest and (small number) % most expensively
priced lots, the average price index would be "more statistically significant"
in scientific terms ( less error margin ).
This is only necessary for items that have at least e.g. 10 distinct lots for
sale.
Why this suggestion ?
Yesterday i noticed one particular seller set all his prices at ( BL avg x 10000
). This caused average price index "lots for sale" to be inflated at least
tenfold.
Someone else suggested he made a mistake in currency.
If this one shopkeeper persists, unwanted "extreme" inflation may occur on several
very common items, and those lots - for sellers not paying attention when adding
to their inventory - might become impossible to sell.
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Voted no.
I do not want BL to remove any data. If you want to suggest *adding* information,
I would be fine with that. (Such as adding the median price.)
To any seller who blindly uses the current For Sale Average to set their prices,
I would have a simple suggestion: Don't.
So, for the suggestion: No. Please do not remove information which is useful
to many of us, just because a few sellers might be using that information in
a silly way (that only hurts themselves).
--
Marc.
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Back when I took stats, trimming extreme outliers was considered a desirable
practice. This would be particularly true if the outlier was not so much a black
swan as a data recording error or false reporting. Does anyone know if this
advice has changed?
In any case, the notion of "removing" data does not seem to fully apply here.
No one is suggesting it be removed from the price guide. Someone interested
in reviewing every data point is free to look at them where they are reported
in the price guide.
Frankly, the only reason I can think of for not making this change is that some
sellers will make fewer and smaller mistakes. That will prevent the rest of
us from enjoying the arbitrage.
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Message is in Reply To: Message Has 1 Reply: 21 Messages in this Thread:  Msg 1 - brick_projects (3656) 96 months ago Jul 20, 2016 to Suggestions
 Msg 2 - FigBits (3564) 96 months ago Jul 20, 2016 to Suggestions
  Msg 3 « - jeslego (1050) 96 months ago Jul 20, 2016 to Suggestions
Msg 4 - FigBits (3564) 96 months ago Jul 20, 2016 to Suggestions
Msg 5 - yorbrick (1185) 96 months ago Jul 20, 2016 to Suggestions
Msg 6 - FigBits (3564) 96 months ago Jul 20, 2016 to Suggestions
Msg 7 - jeslego (1050) 96 months ago Jul 20, 2016 to Suggestions
Msg 8 - FigBits (3564) 96 months ago Jul 20, 2016 to Suggestions
Msg 9 - jedvii (666) 96 months ago Jul 22, 2016 to Suggestions
Msg 10 - yorbrick (1185) 96 months ago Jul 20, 2016 to Suggestions
Msg 11 - jancg (378) 96 months ago Jul 20, 2016 to Suggestions
Msg 12 - ToddMyers (356) 96 months ago Jul 20, 2016 to Suggestions
Msg 13 - jancg (378) 96 months ago Jul 20, 2016 to Suggestions
Msg 14 - Leftoverbricks (2225) 96 months ago Jul 20, 2016 to Suggestions
Msg 15 - garbanzo (322) 96 months ago Jul 20, 2016 to Suggestions
Msg 16 - jancg (378) 96 months ago Jul 20, 2016 to Suggestions
Msg 17 - yorbrick (1185) 96 months ago Jul 20, 2016 to Suggestions
Msg 18 - ToriHada (8887) 96 months ago Jul 20, 2016 to Suggestions
Msg 19 - Made_In_Bricks (3994) 96 months ago Jul 20, 2016 to Suggestions
Msg 20 - FigBits (3564) 96 months ago Jul 20, 2016 to Suggestions
Msg 21 - wildchicken13 (876) 43 months ago Nov 17, 2020 to Suggestions
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USA, Washington
