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| | | Author: | Ohio_Monofigs  | | Posted: | Oct 23, 2022 21:16 | | Subject: | Average Price shown should be Median not mean | | Viewed: | 143 times | | Topic: | Suggestions | | Status: | Open | | Vote: | [Yes|No] | |
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| Using the mean price to display for the "Avg Price" field is misleading. Averages
are prone to be skewed by large values, whereas Median is not.
Look at set 6426244-1. The New Avg Price shown is (currently) $80.91, which seemed
high. When I looked further, I saw there is one listing at $900. When I calculated
the median of this list of values, I determined the median value to be around
$51.15.
Looking at the full dataset, the median value is much more representative of
the "average" value. So my suggestion can be summed up as:
Use the median value for Avg Price
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| | | | | Author: | 1001bricks | | Posted: | Oct 23, 2022 22:18 | | Subject: | Re: Average Price shown should be Median not mean | | Viewed: | 54 times | | Topic: | Suggestions | |
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| | | Looking at the full dataset, the median value is much more representative of
the "average" value.
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Problems:
* This is discussed for 20 years 
* You gave an example, but 100s others may show the exact opposite.
* Median is more suited to discounting high or low results that are suspected
to be anomalous. Problem is, for example for parts, some bulkers have abnormally
low prices. And some shops capitalizing on number of lots do have real (but actual)
very high (some say silly) prices. But both those lowest and highest prices exist
and are 'legit'.
* Who cares the Avg or Median? Would you buy your next used car on Argus?
Me, I'd check the lowest and the highest price (approx) and would find something
in between, depending condition, milage, etc. I wouldn't care if it's
under or above any kind of average.
* Who cares the Price Guide? Buyers don't check them. Almost never. Sellers
shouldn't. I mean, if you're 5% below, you're just average. If you're
50% below (or above) then yes, it'll make a difference. But the average being
at 40$ or 45$ won't make a difference. Your price will.
Frankly?
Leave the PG as is, it's just ONE number, one clue - amongst many others
- your decision should be based on.
My 2 average cents.
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| | | | | | | Author: | Ohio_Monofigs | | Posted: | Oct 24, 2022 11:37 | | Subject: | Re: Average Price shown should be Median not mean | | Viewed: | 33 times | | Topic: | Suggestions | |
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| In Suggestions, 1001bricks writes:
| | | | Looking at the full dataset, the median value is much more representative of
the "average" value.
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Problems:
* This is discussed for 20 years
* You gave an example, but 100s others may show the exact opposite.
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I am not sure what you mean by "show the opposite", because median values will
always be less susceptible to outliers by nature.
| | * Median is more suited to discounting high or low results that are suspected
to be anomalous. Problem is, for example for parts, some bulkers have abnormally
low prices. And some shops capitalizing on number of lots do have real (but actual)
very high (some say silly) prices. But both those lowest and highest prices exist
and are 'legit'.
|
I am not saying high or low prices are not legitimate, but that they are not
representative of the overall pricing data set.
| | * Who cares the Avg or Median? Would you buy your next used car on Argus?
Me, I'd check the lowest and the highest price (approx) and would find something
in between, depending condition, milage, etc. I wouldn't care if it's
under or above any kind of average.
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People use average values when buying selling cars all the time (Kelly Blue Book).
And But also, comparing car prices is also vastly different than Lego due to
price scale and use.
| | * Who cares the Price Guide? Buyers don't check them. Almost never. Sellers
shouldn't.
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This statement is pretty wild to me, because for most elements (besides extremely
common pieces) I check the For Sale and 6 Month Sold average when I am both buying
and selling. When making a purchase, or trying to sell an item, I check the price
guide to see what is fair.
| | I mean, if you're 5% below, you're just average. If you're
50% below (or above) then yes, it'll make a difference. But the average being
at 40$ or 45$ won't make a difference. Your price will.
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But in the example I showed, its a difference between $80 and $50. That is an
enormous difference.
| | Frankly?
Leave the PG as is, it's just ONE number, one clue - amongst many others
- your decision should be based on.
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You aren't wrong, but the point of having a summary is so that people can
get a feel for the data set at a glance. And the mean value is definitely less
representative.
Just hope your average two cents isnt from a data set with low outlier prices,
or you're devaluing your thoughts 
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| | | | | | | | | Author: | 1001bricks | | Posted: | Oct 24, 2022 11:53 | | Subject: | Re: Average Price shown should be Median not mean | | Viewed: | 40 times | | Topic: | Suggestions | |
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| | | | | * Median is more suited to discounting high or low results that are suspected
to be anomalous. Problem is, for example for parts, some bulkers have abnormally
low prices. And some shops capitalizing on number of lots do have real (but actual)
very high (some say silly) prices. But both those lowest and highest prices exist
and are 'legit'.
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I am not saying high or low prices are not legitimate, but that they are not
representative of the overall pricing data set.
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That's the point; they are as valid as other ones (in majority).
Of course if the lowest price is when sold by x1000 then if you wish 1 part it's
not valid.
But this can happen to any other price than the first or the last one.
| | | | * Who cares the Price Guide? Buyers don't check them. Almost never. Sellers
shouldn't.
|
This statement is pretty wild to me, because for most elements (besides extremely
common pieces) I check the For Sale and 6 Month Sold average when I am both buying
and selling. When making a purchase, or trying to sell an item, I check the price
guide to see what is fair.
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You're educated and a seller. A buyer won't.
Much more, the PG may not show VAT or not, sales tax or not, shipping price,
sold in lots (x1000), and even more complicated for Sets (Missing Minifig is
different than Missing Technic Pin), and worse for Used...
Is 10$ shop locally worse or better than 5$ in Germany for example?
Then, what does any average (or mean) mean in this case?
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| | | | | | | | | | | Author: | Ohio_Monofigs | | Posted: | Oct 24, 2022 12:07 | | Subject: | Re: Average Price shown should be Median not mean | | Viewed: | 39 times | | Topic: | Suggestions | |
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| In Suggestions, 1001bricks writes:
| | | | | | * Median is more suited to discounting high or low results that are suspected
to be anomalous. Problem is, for example for parts, some bulkers have abnormally
low prices. And some shops capitalizing on number of lots do have real (but actual)
very high (some say silly) prices. But both those lowest and highest prices exist
and are 'legit'.
|
I am not saying high or low prices are not legitimate, but that they are not
representative of the overall pricing data set.
|
That's the point; they are as valid as other ones (in majority).
Of course if the lowest price is when sold by x1000 then if you wish 1 part it's
not valid.
But this can happen to any other price than the first or the last one.
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I am not sure we will agree on this then I am a data analyst by day, and the
thought of using the mean as a representative value makes my hair stand on end!
| | | | | | * Who cares the Price Guide? Buyers don't check them. Almost never. Sellers
shouldn't.
|
This statement is pretty wild to me, because for most elements (besides extremely
common pieces) I check the For Sale and 6 Month Sold average when I am both buying
and selling. When making a purchase, or trying to sell an item, I check the price
guide to see what is fair.
|
You're educated and a seller. A buyer won't.
Much more, the PG may not show VAT or not, sales tax or not, shipping price,
sold in lots (x1000), and even more complicated for Sets (Missing Minifig is
different than Missing Technic Pin), and worse for Used...
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Definitely correct here! If I became dictator of Bricklink, I would add in an
option to indicate a set is complete EXCEPT minifigs, as well as sort price by
. This would be useful. But you're right that currently
this would be a big issue for sets
| | Is 10$ shop locally worse or better than 5$ in Germany for example?
Then, what does any average (or mean) mean in this case?
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This particular item is solved (for me anyways) by breaking down by currency.
For US users, using USD to sort always shows me the best data. But I didnt consider
EU users trying to sort by Euro, which wouldnt show the same singular seller
location
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| | | | | | | | | | | | | Author: | 1001bricks | | Posted: | Oct 24, 2022 12:45 | | Subject: | Re: Average Price shown should be Median not mean | | Viewed: | 35 times | | Topic: | Suggestions | |
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| | | | | Is 10$ shop locally worse or better than 5$ in Germany for example?
Then, what does any average (or mean) mean in this case?
|
This particular item is solved (for me anyways) by breaking down by currency.
For US users, using USD to sort always shows me the best data. But I didnt consider
EU users trying to sort by Euro, which wouldnt show the same singular seller
location
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This, and the fact that thousands of sotwares and private apps use BrickLink
Average as is.
In short: a Mean Price could be added to the Price Guide, but shouldn't replace
the current Avg.
Apart if BrickLink is preparing a brand new PG, accounting VAT, taxes, lots,
currency, eventual shop fees or currency exchange cost - etc - in this case it'd
be so different that this new PG should be displayed in a different page/URL.
In this case, they can change the definition of Avg also...
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| | | | | Author: | Brick_Qc | | Posted: | Oct 24, 2022 08:23 | | Subject: | Re: Average Price shown should be Median not mean | | Viewed: | 36 times | | Topic: | Suggestions | |
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| In Suggestions, Ohio_Monofigs writes:
| | Using the mean price to display for the "Avg Price" field is misleading. Averages
are prone to be skewed by large values, whereas Median is not.
Look at set 6426244-1. The New Avg Price shown is (currently) $80.91, which seemed
high. When I looked further, I saw there is one listing at $900. When I calculated
the median of this list of values, I determined the median value to be around
$51.15.
Looking at the full dataset, the median value is much more representative of
the "average" value. So my suggestion can be summed up as:
Use the median value for Avg Price
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https://chrome.google.com/webstore/detail/bricktinker/pikfjcohcfpohlckdhdggpcpfdkekomf
The Bricktinker Chrome Extension has shows the median prices. I use it and it's
great.
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| | | | | | | Author: | Ohio_Monofigs | | Posted: | Oct 24, 2022 11:19 | | Subject: | Re: Average Price shown should be Median not mean | | Viewed: | 41 times | | Topic: | Suggestions | |
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Thank you for this suggestion, I will try it out!
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| | | | | | | | | Author: | zorbanj | | Posted: | Oct 24, 2022 15:17 | | Subject: | Re: Average Price shown should be Median not mean | | Viewed: | 46 times | | Topic: | Suggestions | |
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| In Suggestions, Ohio_Monofigs writes:
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Thank you for this suggestion, I will try it out!
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BrickTinker is fantastic. It has a lot of great features besides the median.
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| | | | | | | | | | | Author: | 1001bricks | | Posted: | Oct 24, 2022 16:02 | | Subject: | Re: Average Price shown should be Median not mean | | Viewed: | 48 times | | Topic: | Suggestions | |
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| In Suggestions, zorbanj writes:
| | In Suggestions, Ohio_Monofigs writes:
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Thank you for this suggestion, I will try it out!
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BrickTinker is fantastic. It has a lot of great features besides the median.
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I hope someone read the code, because you can have any information sent anywhere
with an add-on or a greasemonkey+JS...
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USA, Ohio
France, Provence-Alpes-Côte d'Azur
Canada, Quebec