Question on collection values estimate

When I click on my coins, I get two estimates for worth of collection, one is a percentage of the collection's worth based on what I inputed and the other is an estimate of another percentage amount that comes from numista.

Now my question is, do these amounts overlap? Are they for the same coins? Or are they different groups?

Yes, they do overlap.

For most people who've bothered inputting their values the first amount (based on what you input) is likely to be much higher than the second amount (based on the median values input by Numista members), because your more expensive/rare coins likely won't be getting value input by more members any time soon.

Quote: "CassTaylor"​Yes, they do overlap.
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​For most people who've bothered inputting their values the first amount (based on what you input) is likely to be much higher than the second amount (based on the median values input by Numista members), because your more expensive/rare coins likely won't be getting value input by more members any time soon.
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​

​Thanks Cass!

Quote: "CassTaylor"(based on the median values input by Numista members)

​I never understood why they use the median value, and not the average value. The median doesn't say anything.

Take the numbers 1, 2, 97, 5932, 102336.
The median value is 97
The average value is 21673.6
Pretty big difference, if you ask me.

Quote: "ngdawa"​

Quote: "CassTaylor"(based on the median values input by Numista members)

​​I never understood why they use the median value, and not the average value. The median doesn't say anything.
​
​Take the numbers 1, 2, 97, 5932, 102336.
​The median value is 97
​The average value is 21673.6
​Pretty big difference, if you ask me.

Unrealistic example. You are much more likely to see most numbers being pretty close, i.e. 1, 2, 2.25, 2.30, 2.47, 2.75, 247.

The average would be quite high, but does it mean we should consider this to be a valuable coin? Probably not. It's much more likely that someone missed a dot when entering their value. The median gives a much more reasonable result because it ignores such extremes.

What would happen if I put in
1, 2, 2.25, 2.30, 2.47, 2.75, 1, 2, 2.25, 2.30, 2.47, 2.75, 1, 2, 2.25, 2.30, 2.47, 2.75
for one coin only? If written in right sequence, does median value take into account all-multiple values from single entry? Well, it works nice with piling emails into single field when programming.

Quote: "Houseofham"

Quote: "ngdawa"

Quote: "CassTaylor"(based on the median values input by Numista members)

​​​I never understood why they use the median value, and not the average value. The median doesn't say anything.
​​
​​Take the numbers 1, 2, 97, 5932, 102336.
​​The median value is 97
​​The average value is 21673.6
​​Pretty big difference, if you ask me.

​Unrealistic example. You are much more likely to see most numbers being pretty close, i.e. 1, 2, 2.25, 2.30, 2.47, 2.75, 247.

Well ​of course it's unrealistic. I just wanted to point out the difference between the median value and the average value.

In your example 2.30 is the median, and the average is 37.11. Still a big difference, don't you think?

So, which do you think the market price would be, 2.30 or 37.11?

Quote: "Houseofham"​So, which do you think the market price would be, 2.30 or 37.11?

​Is the counter for giving an average price paid for a coin, or for a most likely paid price?

You don't have to make it peronal, I'm just saying that the median is pointless.

Something else that's been brought up is to obsolete the lowest and highest number, and then make the value.
That would leave with a median with still 2.30, but the average would be 2.354, which would be more accurate.

It's an estimate of the price you would most likely be expected to pay. The average is useless -- it is affected too much by the extremes on either end of the spectrum, even if you ignore the highest and the lowest values (which just makes it a little more like the median). There is nothing personal about it, it's just math. I'll give you a couple more examples to demonstrate this:

1) 1.75, 1.95, 2, 2, 2.25, 2.30, 2.45, 8, 10
2) .05, .15, 2, 2, 2.25, 2.30, 2.45, 2.75, 3

In both cases, 9 values have been entered. Let's say we ignore the highest and the lowest. The median is the same -- 2.25. Now, let's look at the averages. In the first case, it's 2.99 -- over-inflated by the high In the second case, 1.99 -- over-deflated by the low .15.

Dunno about the rest of you guys ... But my head is hurting lol

Mike

Quote: "brismike"​Dunno about the rest of you guys ... But my head is hurting lol
​
​Mike

​lol, mine too..

Apart of how it is calculated....
What does it signify???

It is as the Numista Rarety Index.

Who cares?
And does who care.... Think twice...
the world is bigger than Numista.

have you been drinking?

Just added a common circulating coin to the catalogue.......so NRI is 97......
It means nothing.......

Quote: "Houseofham"​have you been drinking?

​+1

Quote: "PhilipBe"​
​
​Just added a common circulating coin to the catalogue.......so NRI is 97......
​It means nothing.......

​what coin is it?

I think I remember reading that the values are only displayed once several values are entered and that the top and bottom values are discounted to remove the instance of extremes throwing things out. If this was the case then the median from the example originally offered by Houseofham is 2.3 and the mean is 2.35.

Of course no system is perfect, but as more values are entered then both systems will get closer to each other.

Quote: "neilithicman"​I think I remember reading that the values are only displayed once several values are entered and that the top and bottom values are discounted to remove the instance of extremes throwing things out. If this was the case then the median from the example originally offered by Houseofham is 2.3 and the mean is 2.35.
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​Of course no system is perfect, but as more values are entered then both systems will get closer to each other.

​You're right, minimum 4 values entered by members to have one median displayed. Lowest and highest values are not used for the median calculation.

The more values are entered, the more the median value should approach a realistic estimate.

Next update should involve a logic relation between values: a higher grade would not have a lower value than a lower grade. Having more listings to match sales from auction houses would also be nice, even thoug it's a bit harder to implement.