Same stone to 4 labs - Is it a wash?

[valeria101]

Date: 10/21/2005 3:20:11 AM
Author: diamondsbylauren

I have seen cases of EGL stones to be two grades off GIA - based on my own observations. It is very rare , but it does happen on both color and clarity. Testing 16 stones could not eliminate this possibility.

Small sample (expensive as it was to acquire) may not be representative by statistics alone... what is

Good to put things into perspective, as you say below. If anything, these results are good enough to prove that there is a material difference between grades by different labs and that prices follow it for better or worse, on average. Perhaps this can be read bots as ''only ever consider GIA'' or ''don''t expect the same grades to mean the same regardless of lab'' or ''take grading with a grain of salt'' etc. To each his own. Are these fair interpretations?


I''ve seen cases of stones trading at 30%+ less with EGL reports as compared to GIA- again ,primarily in cases of higher priced, larger diamonds.

True enough, ''seen among Diamonds by Lauren listings every now and then. Nice ones

...

I was never trying to invalidate the value of the study- only to put it in perspective

Well, I might be wrong, but feel safe saying that at least a few times this study has been taken as if to push a deterministic value for the price differential between two identical grades by two different labs''. The text itself doesn''t seem to encourage such simplistic interpretation though. Before seein this in some post (most likely, where else?) it would not have crossed my mind

Just a thought...

Taking a step back from the whole story, it is strange that different labs did not insist on following the same grading system and practice. From a different perspective, this is rather interesting even if trivia fact of life for you

 

[oldminer]

Hey guys, you are taking a very valuable tool for creating confidence in the description of a diamond and trashing it thoroughly, and in public. The GIA, and AGS, and many small appraisers like myself, grade diamonds accurately enough that phony cert houses cost us a lot of business, but in the overall the market is very smart and prices meet the actual quality of the diamond in nearly all cases where competition exists.

The GIA and other huge labs have a weakness in their grading because diamonds are graded by humans. When you have 100+ graders making color grades you always have some variation in the outcome no matter how well they were trained. The cure is 10 highly accurate machines performing consistent color grading under the supervision of a small number of highly trained, well supervised experts. There would be virtually no error under such a scientific operation. That time is close at hand. It has arrived in our office already.

Meanwhile, you are arguing over the number of fairies able to standi on the head of a pin. Diamonds are well graded by the two major US labs that have been discussed here and graded equally as well by many secondary and tertiary players. There are a couple wildiy successful secondary labs with questionable grading and I think consumers who read Pricescope are forewarned. What benefit are we creating here? This horse is well shot and pretty darned dead!

The 16 diamond review we did is a very sound tool used properly. It is telling on how prices are created and is statistically sound for its intended use. It was not made to denigrate labs, but to prove pricing corrects potential lab error.

 

[kenny]

One horse ain't dead:
The original question.
I still don't hear an answer.

Same stone that got 4 different results from four labs . . .
Will the price be about the same for all four?

In other words do market forces make lab choice a wash when it comes to price?

 

[Regular Guy]

Date: 10/21/2005 7:46:02 AM
Author: kenny
One horse ain''t dead:
The original question.
I still don''t hear an answer.

Same stone that got 4 different results from four labs . . .
Will the price be about the same for all four?

In other words do market forces make lab choice a wash when it comes to price?

Kenny, I thought Dave tried to take a pretty dead on crack at an answer:

"The GIA, and AGS, and many small appraisers like myself, grade diamonds accurately enough that phony cert houses cost us a lot of business, but in the overall the market is very smart and prices meet the actual quality of the diamond in nearly all cases where competition exists."

 

[denverappraiser]

Date: 10/21/2005 7:46:02 AM
Author: kenny
One horse ain''t dead:
The original question.
I still don''t hear an answer.

Same stone that got 4 different results from four labs . . .
Will the price be about the same for all four?

In other words do market forces make lab choice a wash when it comes to price?

No.

Market forces certainly apply but there are important variables beyond the gemological properties of the stone.

Neil Beaty
GG(GIA) ISA NAJA
Professional Appraisals in Denver

 

[kenny]

One yes.
One no.

 

[kenny]

I didn''t start this thread to stir up a pot.

I started it because I am a customer trying for form a deeper opinion.
I''m 49 years old and have purchased 6 diamonds in the 6 months I have been reading PS.
I am entering my peak earning years and expect to buy more, as gifts or for myself.

My bias was for AGS or GIA exclusively.
Sure it costs more, but it gave me a warmer fuzzier feeling I was willing to pay extra for since I was a novice.
Now I am reconsidering stones from the other labs, but only if I have done a lot of homework and know how to look for the occasional good stone.

The big remaining uncertainty for me is price.
Is lab choice already fully factored in?
Is it a wash?

 

[Garry H (Cut Nut)]

Date: 10/21/2005 7:27:53 AM
Author: oldminer
This horse is well shot and pretty darned dead!

The 16 diamond review we did is a very sound tool used properly. It is telling on how prices are created and is statistically sound for its intended use. It was not made to denigrate labs, but to prove pricing corrects potential lab error.

Thanks Dave. You said it all.

 

[oldminer]

You can make a case that shows a phony or badly done lab report might mislead a consumer into a false belief about quality. That set of consumers that are misled often also pay the wrong price for a diamond, mostly because they are not smart shoppers. Smart shoppers get the right price more often.

You can also make the case, based on our 16 diamond study, that smart shoppers get fair pricing regardless of the lab and the erratic nature of grading.

It IS a wash for smart shoppers and the educated, careful consumer. The opposite applies to impulsive undereducated or naive buyers. They are lambs going to the slaughter and always will be. Even when they buy a diamond with total knowledge of "the true grade" these folks rarely get the best range of price. It is a tough world out there for the weak or uninformed.

 

[strmrdr]

Date: 10/21/2005 7:27:53 AM
Author: oldminer
The cure is 10 highly accurate machines performing consistent color grading under the supervision of a small number of highly trained, well supervised experts. There would be virtually no error under such a scientific operation. That time is close at hand. It has arrived in our office already.

That would make me very happy.
It will take a lot of proof to get it accepted.
I for one hope it will be proven.
When it comes to measuring diamond performance there are too many variables for one machine to be the end all of diamond performance grading in my opinion but color grading and to a somewhat lesser extent clarity grading is the perfect place for a machine.

In some ways I wish that they had been put in 2 different machines.
I think the performance measurement issue will hold back acceptance of the color and clarity grading abilities.

Is it possilble to have it do a color and clarity report without reporting the performance testing score?

 

[oldminer]

One of the many varieties of possible operation is a full report without any mention of Light Behavior. We, AGA, have chosen not to provide that sort of report using ImaGem. We still do those limited reports the old fashioned way. All grading of color and clarity is supervised by our gemologists, even when ImaGem is being utilized. There will be a small percentage of diamonds that will not be graded properly by the present level of technology. I have said before that it cost millions to get where we are and it would be an inordinant further high cost to make only a tiny incremental improvment at this stage. Possibly, more will be done in the future, as is the common practice of all technological maturation. At the moment, we believe about 97% to 98% of the color grading the ImaGem GL3000 / GL3100 offers is the same grade we would have placed on it the old way........................with master diamonds and our eyes. The one best thing is that the machine produced grade is always the same morning, noon, and at 5pm, too. Humans have variance from tired eyes or lack of diligence.

A very well respected gemologist friend of mine, is taking a test drive of one of the ImaGem devices for his lab. He wants to grow into a larger lab, but does not want the "problem" GIA and other large labs have with inconsistent grading due to the inability to manage so many graders properly. He said his idea of a large lab would be 10 GL3100 machines all grading with consistent, tireless results. I agree that this would be the sort of objective grading standard that will bring the diamond business to the next level. Everyone in the room where he was speaking seemed to understand the elegant nature of the concept. You don''t have to be a scientist to understand that if the GL3100 technology is very good, things will happen to diamond grading and standards.

I know the desire for further details on Light Behavior. It will come in due course. I have been a patient participant for 8 years in this. One just does not go as fast with a big business as with a small one. Measured steps, careful evaluations. These are the keys to this process. Please bear with me.

 

[diamondsbylauren]

Kenny- you DID ask a question. Well, looking it over, the question is almost moot.
First of all, even though a two grade difference is possible- and I''ve personally seen it- it is by no means common- so it''s hard to assume that the same diamond would get I SI2 from AGS, and F/VS1 from any of the numerous EGL''s.

You pointed out some very important points which make this question impossible to actaully frame. Such as point #5

5. The same stone will have a different price in different markets, internet, B&M, Beverly Hills B&M, etc.

For example, it''s difficult to imagine any dealer actually stocking such 4 stones.
Certainly we can all agree that different dealers will treat the same situation differently- if there''s a weak SI1, some dealers will charge less- others will charge just what they would for any SI1.

See, your question ultimately was about the price- I think price is an important consideration to most people buying diamonds- and it is here where making assumptions- or drawing conclusions can get one into trouble.
If 14% was the average difference in price between GIA and EGL USA, then it could mean that there was on that was the same price, and one at 28% less.

 

[RADIANTMAN]

David - your point about average price differentials is right on.

Kenny - if your question centers on whether, employing pricescope''s survey, you can figure out the relative value of stones with reports from different labs sight unseen, then the answer is you can''t. An EGL stone can be overpriced at a 30% discount from GIA, and it can be priced fairly at no discount from GIA. There''s no way to tell without examining the diamond yourself (assuming you have the expertise to do so)

Internet shopping would be easier if certifying a diamond truly turned it into a fungible commodity, but it doesn''t. That''s why paying a premium to purchase from a knowledgable and trustworthy vendor is generally well worth it.

 

[denverappraiser]

Date: 10/21/2005 4:23:23 PM
Author: RADIANTMAN

That''s why paying a premium to purchase from a knowledgable and trustworthy vendor is generally well worth it.

Using the services of a skilled appraiser is often helpful.

Neil Beaty
GG(GIA) ISA NAJA
Professional Appraisals in Denver

 

[diamondsbylauren]

Dave- I am all for everyone feeling comfortable with GIA or AGS- these two labs form the backbone of diamond grading today.
I don't know how many people know this, but the technology for grading diamonds by machine was "perfected" years ago. To this point, GIA has maintained that diamonds are best judged by human eyes. In either case, there will be some diamonds which are much more likely to be misgraded.
I've seen VS2 sized imperfections which were eye visible- yet the diamond was correctly graded VS2.
I've seen stones that lookd like a J from behind, but faced up like an L- others that looked like an H when you faced them up

Garry- I realize a lot of money was spent to make the study possible- and it was done to benefit the readers.
You asked about EGL,and which one I used.
In an AMAZING coincedence, I just got a diamond back from GIA-it's a .93 Square Emerald Cut. This diamond has a "Prelim" from EGL- yes, EGL USA.
The EGL grade was F/VS1- GIA graded this diamond H/VS1.

So here is a case of two grades color difference between GIA and EGL USA. The concern would be that someone not in the business who reads the study will assume this is impossible.


Thank you Stan!

PS- I would say that studies value is enhanced by this "beating a dead horse" thing.
If it actually was a "dead" horse I don't think so many people woud be interested- the study causes us to talk about it, and that simply enhances it's usefulenss

 

[MissAva]

Date: 10/21/2005 5:23:49 PM
Author: diamondsbylauren
Dave- I am all for everyone feeling comfortable with GIA or AGS- these two labs form the backbone of diamond grading today.
I don''t know how many people know this, but the technology for grading diamonds by machine was ''perfected'' years ago. To this point, GIA has maintained that diamonds are best judged by human eyes. In either case, there will be some diamonds which are much more likely to be misgraded.
I''ve seen VS2 sized imperfections which were eye visible- yet the diamond was correctly graded VS2.
I''ve seen stones that lookd like a J from behind, but faced up like an L- others that looked like an H when you faced them up

Garry- I realize a lot of money was spent to make the study possible- and it was done to benefit the readers.
You asked about EGL,and which one I used.
In an AMAZING coincedence, I just got a diamond back from GIA-it''s a .93 Square Emerald Cut. This diamond has a ''Prelim'' from EGL- yes, EGL USA.
The EGL grade was F/VS1- GIA graded this diamond H/VS1.

So here is a case of two grades color difference between GIA and EGL USA. The concern would be that someone not in the business who reads the study will assume this is impossible.


Thank you Stan!

PS- I would say that studies value is enhanced by this ''beating a dead horse'' thing.
If it actually was a ''dead'' horse I don''t think so many people woud be interested- the study causes us to talk about it, and that simply enhances it''s usefulenss

Do you really think that likely? What are you basing that on? Just because one is not in the business does not mean they are incapable of logical thoughts.

 

[kenny]

Hey DBLDavid
Maybe that stone got two grades higher from EGL because the bribe was larger.

 

[diamondsbylauren]

Hi Matatora,
How are you?
What I meant was that people in the diamond business would likely understand the difference between GIA and EGL. This has absolutely noting to do with anyone''s ability to draw logical conclusions. It''s simply a matter of being familiar with a particular industry''s standards.
For example, I don''t know which company is the best at grading....bowling ball durability.
Ask a guy who owns a bowling alley, he might have an idea.


Kenny,
When I purchased the .93 it came with the EGL- from a small, very honest seller. I paid ( at the time) nowhere near the price of a F/VS1 with a GIA.
I really do not think he would be in a position to bribe anyone, or anything.
We''ve simply had the diamond for a long time, maybe due to my well known feelings about non GIA reports- that''s why I finally bit the bullet and sent it off to GIA- just a weird coincidence that it came back today.

 

[SparklyThing]

Hi, I don't post much, but felt I should let everyone know EGL Israel isn't that bad, at leats not in my experience. I tried out a F SI1 and before I bought it got it independently appraised and got the exact same thing. I was pretty impressed after hearing all the bad things about them.

 

[Garry H (Cut Nut)]

Date: 10/21/2005 4:22:24 AM
Author: Garry H (Cut Nut)

Date: 10/21/2005 3:20:11 AM
Author: diamondsbylauren

The lab grades did however confirm some of the market myths, such as EGL USA color grades can be softer and AGSL clarity grades can be stricter than GIA-GTL. However, we found no support for reports of EGL USA color grading being more than one grade different to the other labs. In fact all lab grades were within a single grade of difference for color or clarity.

I have seen cases of EGL stones to be two grades off GIA - based on my own observations. It is very rare , but it does happen on both color and clarity. Testing 16 stones could not eliminate this possibility.David was this EGL or EGL-USA? And very rare might not be a statistically significant issue anyways.

EGL graded diamonds are currently offered within the trade at 9% - 15% lower than the same grade GIA-GTL stones.

I''ve seen cases of stones trading at 30%+ less with EGL reports as compared to GIA- again ,primarily in cases of higher priced, larger diamonds. David was this EGL or EGL-USA? And please remeber that Leonid did not just make up these numbers - they are based on listed prices of hundreds or even thousands of stones with the same table size and depth %''s data for the individual diamonds.
So this is not a stone here or a stone there - and it was a factual real stones offered for sale and focused on the size and color range that we judged to be most applicable to the consumers that we are acting as advocates for. You have mentioned eg''s of big and rare stones etc - we are not considereing such goods for the reasons just given.

The study takes a good step in the type of education which benefits the consumer and the trade- it was conducting using a good method for the stones tested. If it was done with a broader cross section of diamonds , in a wider variety of shapes colors and sizes, it could give a more balanced veiw. we can use the same tight statistical controls with fancy shapes - as you know there are too many variables - and we did the most interesting sizes for the common requests and stones we see removed (ie sold).
I''d also like to re- sbmit the same diamond to each lab a number of times blind- and see if each lab gives it the same grade every time. If you read the report thoroughly you will see this happened by accident with stone 17 - it was sent to GIA again by clerical mistake and got a different clarity grade. Bill Boyajian was good enough to pull the data and found that on both occasions they noted it was a border line call - the vendor concurred.
I was never trying to invalidate the value of the study- only to put it in perspective
with the help of the vendors and loans of their stones, this survey, we believe the largest ever publicly reported, was conducted entirely at Pricescopes expense. Sure we would like to send 2,000 stones, and haggle on each one - resubmit them to same lab in different countries etc etc - but the shipping, insurance and lab fees, time etc are prohibitive.

So unless you or someone else wants to do better.......

You missed this i think David

 

[kenny]

DBLDavid
Goodness, the bribe comment was a joke.

Didn''t you read the threads today and yesterday about the head of GIA resigning over a bribery scandal?
I put a smiley in, and everything.

 

[valeria101]

Yeah....




Prices adjust (so a chance of cert may chance the grades on paper but not chance prige all the way).


I don''t think I gave a one word straight answer in my life!

In this case, I''d rather write a book... there is allot more to the story, IMO. For exammple, there are lots of diamonds sold without a lab report,how about them? And some lab reports are made to demonstrate some reason for a price premium specifically (i.e. cut quality - by GCAL, AGS some EGL) and that is a different part of the story.

The amazing thing for me in all this is that whichever way it goes, this is not something easy (if possible) to tell from the buyer''s shoes. The system may not be perfect, but comparing sheets of paper seems easier than learning to grade diamonds bootleg over the counter. So lab reports are a good thing.

Just 0.2

What is the use of this discussion anyway?

 

[diamondsbylauren]

Date: 10/21/2005 8:50:04 PM
Author: Garry H (Cut Nut)

Date: 10/21/2005 4:22:24 AM
Author: Garry H (Cut Nut)

Date: 10/21/2005 3:20:11 AM
Author: diamondsbylauren

The lab grades did however confirm some of the market myths, such as EGL USA color grades can be softer and AGSL clarity grades can be stricter than GIA-GTL. However, we found no support for reports of EGL USA color grading being more than one grade different to the other labs. In fact all lab grades were within a single grade of difference for color or clarity.

I have seen cases of EGL stones to be two grades off GIA - based on my own observations. It is very rare , but it does happen on both color and clarity. Testing 16 stones could not eliminate this possibility.David was this EGL or EGL-USA? And very rare might not be a statistically significant issue anyways.
Garry- the stone yesterday was graded by EGL USA, and the NY GIA office- and it's certianly statistically signifigant to me!

EGL graded diamonds are currently offered within the trade at 9% - 15% lower than the same grade GIA-GTL stones.

I've seen cases of stones trading at 30%+ less with EGL reports as compared to GIA- again ,primarily in cases of higher priced, larger diamonds. David was this EGL or EGL-USA? And please remeber that Leonid did not just make up these numbers - they are based on listed prices of hundreds or even thousands of stones with the same table size and depth %'s data for the individual diamonds.
So this is not a stone here or a stone there - and it was a factual real stones offered for sale and focused on the size and color range that we judged to be most applicable to the consumers that we are acting as advocates for. You have mentioned eg's of big and rare stones etc - we are not considereing such goods for the reasons just given.
What if a particular consumer was interested in something else- does this study NOT apply to them?
Also- if the prices were off a databse list it is likely that the stats are skewed- for example if many companies list the same GIA diamond at slightly different prices- how many of the EGL stones were offered by multiple vendors? How many EGL stones were used in the broader price comparison anyway?
The study takes a good step in the type of education which benefits the consumer and the trade- it was conducting using a good method for the stones tested. If it was done with a broader cross section of diamonds , in a wider variety of shapes colors and sizes, it could give a more balanced veiw. we can use the same tight statistical controls with fancy shapes - as you know there are too many variables - and we did the most interesting sizes for the common requests and stones we see removed (ie sold).
I'd also like to re- sbmit the same diamond to each lab a number of times blind- and see if each lab gives it the same grade every time. If you read the report thoroughly you will see this happened by accident with stone 17 - it was sent to GIA again by clerical mistake and got a different clarity grade. Bill Boyajian was good enough to pull the data and found that on both occasions they noted it was a border line call - the vendor concurred. I did notice that. I feel that would happen in many cases of resubmission
I was never trying to invalidate the value of the study- only to put it in perspective
with the help of the vendors and loans of their stones, this survey, we believe the largest ever publicly reported, was conducted entirely at Pricescopes expense. Sure we would like to send 2,000 stones, and haggle on each one - resubmit them to same lab in different countries etc etc - but the shipping, insurance and lab fees, time etc are prohibitive.

So unless you or someone else wants to do better.......

The study is an interesting exercise- done with good intentions. I'm sorry if a critical discussion of the study might seem..insulting to those who went the the trouble and expense of doing it.

From the standpoint of how each lab rated each particular diamond- it's quiite interesting, but I don't feel it's possible to draw specific pricing inferences.
I think it's of more use to those in the trade.

I'd be happy to log experiences such as the one which happened today ( the .93 Asscher which EGL graded F and GIA graded H)

I have a few more diamonds which have EGL reports. I intend to submit these to GIA.
I'll be happy to post the results after I get the GIA reports.
I'd also be happy to send these off to AGS if you folks would like to incororate the results into the study

You missed this i think David

 

[valeria101]

Date: 10/21/2005 3:20:11 AM
Author: diamondsbylauren


I''d be happy to log experiences such as the one which happened today ( the .93 Asscher which EGL graded F and GIA graded H)

I have a few more diamonds which have EGL reports. I intend to submit these to GIA.
I''ll be happy to post the results after I get the GIA reports.
I''d also be happy to send these off to AGS if you folks would like to incororate the results into the study

This sounds pretty cool!

The pricing bit of the existing sample will not be there, but the main point (difference of grading practice between labs) will, and that is rather scarce in open sources. If there''s good data (pairs of reports should be just that), than finding an explanation and use for it should come out too. Can''t wait!

 

[Garry H (Cut Nut)]

Date: 10/21/2005 3:20:11 AM
Author: diamondsbylauren


I have a few more diamonds which have EGL reports. I intend to submit these to GIA.
I''ll be happy to post the results after I get the GIA reports.
I''d also be happy to send these off to AGS if you folks would like to incororate the results into the study

David this would not be a balanced study.
It is too easily biased. We did not use such sloppy procedures.

 

[valeria101]

Date: 10/22/2005 5:21:11 AM
Author: Garry H (Cut Nut)

Date: 10/21/2005 3:20:11 AM
Author: diamondsbylauren


I have a few more diamonds which have EGL reports. I intend to submit these to GIA.
I''ll be happy to post the results after I get the GIA reports.
I''d also be happy to send these off to AGS if you folks would like to incororate the results into the study

David this would not be a balanced study.
It is too easily biased. We did not use such sloppy procedures.

Hopefully this question is not missplaced...
I can see how digging out extreme cases will appear as relative outliers to the existing sample - probably not hard given the small sample. Can selection bias change this?

The pricing comments to the existing Pricescope article were drawn from a different sample than the grading report - and that can still be done, of course. With the same rapport of association between the grading and pricing results

Worse still

I may have missed the point of this thread too! Pricing does not seem to be ''consistent'' for the same grades from the same lab or for the same diamond by different sellers... and this adds a grain of salt to the association between the pricing stats and the survey bit in Pricescope''s study. ''Thought that was obvious anyway.




Perhaps this is ... silly. I know nothing of the commercial decissions in favor of one or another lab. Perhaps I should know more statistics than I actually do.

 

[Regular Guy]

Date: 10/22/2005 7:04:55 AM
Author: valeria101
Perhaps this is ... silly. I know nothing of the commercial decissions in favor of one or another lab. Perhaps I should know more statistics than I actually do.

Aye, me too.

But, a few points are correct, I think. Having taken research methodology level I, stats (also level I, but more than once) and sold text books in the area (does that count?), I do know that stats, research methods, and math are each different, but intricately connected.

Re stats, as Garry says, procedures, and hypothesis construction is very important to establish "validity," which is another way to say: "Do you trust these results," which is, after all, why you do the study. I think in the original presentation of the study, some useful comments followed it, to indicate that this was a helpful "lay up" to what could be a follow up. But a follow up...those guys in government often make fun of of studies that do things like measure observations of people to show that if you put too much salt in a stew it actually turns bitter and bad, or something like that, so whose to say a follow up is needed.

Someone with greater stat & research methodology chops could comment and benefit, but there is a known thing related to "power" and statistical significance. It has to do with the fact that you can have as little as 40 some odd people in a room, and make what seem to be provocative guesses about matching birthdays, without having 365 people there. (Just where is Marilyn Vos Savant when you need her!) As I understand it, the thing is, with not a great deal more diamonds tested than were tested...I'm not sure if it would be triple the number, and possibly double the number, statistical validity -- as I understand it from the point of view of established research methodology -- could have been established. Alternately, it's extremely reasonable to initiate any study with a test of the waters to see how best to go forward. Though someone else could more knowledgeably speak to this better than I, I think the Pricescope study was somewhere in between. The language to say how conclusive would have to come from someone more studied in this than me.

 

[diamondsbylauren]

Date: 10/22/2005 5:21:11 AM
Author: Garry H (Cut Nut)

Date: 10/21/2005 3:20:11 AM
Author: diamondsbylauren


I have a few more diamonds which have EGL reports. I intend to submit these to GIA.
I''ll be happy to post the results after I get the GIA reports.
I''d also be happy to send these off to AGS if you folks would like to incororate the results into the study

David this would not be a balanced study.
It is too easily biased. We did not use such sloppy procedures.

Ana- your intentions are exactly in the right place, but what exactly are "statistics" good for?
Well, someone who understands the subject of the statistics in the first place, can extrapolate numbers, or patterns from the statistics. Of course we all know if cases where statistics can be turned around to skew results.
I''m not saying that''s happened intentionally here- it''s simply difficult to draw meaningful conclusions on such a narrow subject group- both in number and variety.

I have a very solid handle on the Gem Lab situation- having dealt with thousands of stones from both EGL and GIA- I''d say looking at patterns coulfd be informative, but I would not draw concrete conclusions- that is to say, conclusions which would allow me to make buying decisions. ie " Oh here''s a 5 carat G/VS1 wifth an EGL USA report- I should offer 14% less than I would if it had a GIA" Not with MY money.

Garry, I owned a diamond with an EGL USA report- one which I did not commission myself. I subsequently sent the diamond to GIA and got their opinion. I didn''t do it with this conversation in mind- We submitted the diamond to GIA weeks ago! If you have any doubt about the diamond, I have offered to submit it to AGS- that would cetainly prove the diamond exists.
Plus I''d be quite interested to see what color they call it!
What exactly about this situation is "sloppy"?
The other diamond I was thinking of is a 2.74 Oval - also purchased with an EGL USA report.
It would seem to me that such stones would simply add more depth to the study- one of the things I wish the study had is a greater diversity of shapes and color.

 

[valeria101]

Date: 10/22/2005 5:15:23 PM
Author: diamondsbylauren

Ana- your intentions are exactly in the right place, but what exactly are 'statistics' good for?

Trying to explain below...


Well, someone who understands the subject of the statistics in the first place, can extrapolate numbers, or patterns from the statistics. Of course we all know if cases where statistics can be turned around to skew results.
I'm not saying that's happened intentionally here- it's simply difficult to draw meaningful conclusions on such a narrow subject group- both in number and variety.

Hm... I should have been more clear perhaps.

Taking your words:

"someone who understands the subject of the statistics in the first place, cannot extrapolate numbers, or patterns from the statistics."

pretty much as you said in an earlier post on this thread:

"... attempting to caluculate a formula which accurately indicates a repeatable, consistent price differential between a diamond with a GIA report, and one with any other is impossible."


It may be just my reading, but it seems that one point of dissent earlier on this thread was about how to interpret an average. You'd think this is simple, but with trully scarce data the temptation to overinterpret them gets easily out of hand. More often than not this is even needed in order to make any use at all of the data. Nearly anywhere in Social Sciences data is really bad - so bad, that statisticians (I mean the mathematicians doing statistics, not those specializing in applied statistics) have a good laugh at it. It is extremely difficult to work with scarce data and their interpretation... well, makes alot more ink flow than the math itself.

To me, this is exciting stuff

I don't think your extra data points could indeed be blended into the existing sample, just like Pricescope's sample did not fit with earlier attempts to quantify grading consistency. But if these are the worst examples you have encountered, they would help get an idea of exactly how good or bad the existing results are. Also, I thought that a particular point of the existing survey would benefit: the link between the survey of grade consistency and the pricing which is drawn from a different and much broader sample. Between the two, the relation is only by intuitive association if a confidence interval for the survey data cannot be drawn. Adding some extreme examples of grading disagreement would help interpret the results at their worst. And that 'worst' can't be that bad, I'd say. Nothing unusual for small sample studies

This is what the 0.2 was all about.

 

[diamondsbylauren]

Date: 10/23/2005 7:13:14 AM
Author: valeria101

Date: 10/22/2005 5:15:23 PM
Author: diamondsbylauren

Ana- your intentions are exactly in the right place, but what exactly are ''statistics'' good for?

Trying to explain below...


Well, someone who understands the subject of the statistics in the first place, can extrapolate numbers, or patterns from the statistics. Of course we all know if cases where statistics can be turned around to skew results.
I''m not saying that''s happened intentionally here- it''s simply difficult to draw meaningful conclusions on such a narrow subject group- both in number and variety.

Hm... I should have been more clear perhaps.

Taking your words:

''someone who understands the subject of the statistics in the first place, cannot extrapolate numbers, or patterns from the statistics.''

Hi Ana- What I said was that if someone had the knowledge they could use the statistics in some sort of a meaningful way.
pretty much as you said in an earlier post on this thread:

''... attempting to caluculate a formula which accurately indicates a repeatable, consistent price differential between a diamond with a GIA report, and one with any other is impossible.''


It may be just my reading, but it seems that one point of dissent earlier on this thread was about how to interpret an average. You''d think this is simple, but with trully scarce data the temptation to overinterpret them gets easily out of hand. More often than not this is even needed in order to make any use at all of the data. Nearly anywhere in Social Sciences data is really bad - so bad, that statisticians (I mean the mathematicians doing statistics, not those specializing in applied statistics) have a good laugh at it. It is extremely difficult to work with scarce data and their interpretation... well, makes alot more ink flow than the math itself.

To me, this is exciting stuff

I don''t think your extra data points could indeed be blended into the existing sample, just like Pricescope''s sample did not fit with earlier attempts to quantify grading consistency. But if these are the worst examples you have encountered, they would help get an idea of exactly how good or bad the existing results are. Also, I thought that a particular point of the existing survey would benefit: the link between the survey of grade consistency and the pricing which is drawn from a different and much broader sample. Between the two, the relation is only by intuitive association if a confidence interval for the survey data cannot be drawn. Adding some extreme examples of grading disagreement would help interpret the results at their worst. And that ''worst'' can''t be that bad, I''d say. Nothing unusual for small sample studies

This is what the 0.2 was all about.

Garry- If you''re out there- I''ve responded to your questions.
I''d be very interested in your response- or are you going to simply bring up points and run away, as you have done in the past........