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#1
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Why not do a real scientific test?
Ed. Stoebenau wrote: James Higby wrote: The old-timers (gotta be careful when I use that term) like to go around saying, "Well, in my day, a coin was either uncirculated or it wasn't." But let's take all those guys in a time machine back to 1955 and set them down at a table upon which are laid out 500 uncirculated silver dollars. Then let's instruct them to sort those coins into two piles, the ones above average and the ones below average. Very easily done, no doubt in my mind. Then let's instruct them to sort each of those piles into several sub-piles until they had a total of eleven piles, in ascending order of desirability. My money bets on them being quite capable of completing the task. Thus the monster has always existed. The only thing different is that it now has a name and a face. Sure, and everyone's piles will all be different from one another. Ask them to do the task again, and they'll be different from what they got before. There are gradiations within grades, but it's a multidimensional continuum and not something which anyone can do at the precision assumed in the current number of uncirculated grades. It would be quite easy to do a scientific test that shows how much precision an experienced coin collector or dealer actually has. Have someone put some sort of numbered label on each coin, covering up the label if the coins are in containers (post-it-notes?), writes down which number is which grade. The numbers should be assigned by a dice roll or by getting numbers from the hotbits website. That person goes away with the list so as to make it a double-blind test. Then the person being tested tries to grade the coins, writing down the results. Compare the two lists, and it's a simple matter of statistics to find out that that person has, say, a 95% chance of being within 2 grades of the label. This is, of course the combined error of the testee and the original grader. Repeat for several coin collectors / dealers, and you will know that most coins are plus or minus N grades from what is on the label. Then publish it as an article in a cion magazine, inviting readers to repeat the test and send you the results. You could even find out which of you is the best and the worst at grading coins! |
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#2
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snip Repeat for several coin collectors / dealers, and you will know that most coins are plus or minus N grades from what is on the label. Then publish it as an article in a cion magazine, inviting readers to repeat the test and send you the results. You could even find out which of you is the best and the worst at grading coins! Did anybody happen to save the Coin World slabbing test printed in the November 17th 2003 issue? I've googled everything I could think of and can't find it online. The PNG/ICTA survey is easily found however. |
#3
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wrote in message ... Ed. Stoebenau wrote: James Higby wrote: The old-timers (gotta be careful when I use that term) like to go around saying, "Well, in my day, a coin was either uncirculated or it wasn't." But let's take all those guys in a time machine back to 1955 and set them down at a table upon which are laid out 500 uncirculated silver dollars. Then let's instruct them to sort those coins into two piles, the ones above average and the ones below average. Very easily done, no doubt in my mind. Then let's instruct them to sort each of those piles into several sub-piles until they had a total of eleven piles, in ascending order of desirability. My money bets on them being quite capable of completing the task. Thus the monster has always existed. The only thing different is that it now has a name and a face. Sure, and everyone's piles will all be different from one another. Ask them to do the task again, and they'll be different from what they got before. There are gradiations within grades, but it's a multidimensional continuum and not something which anyone can do at the precision assumed in the current number of uncirculated grades. It would be quite easy to do a scientific test that shows how much precision an experienced coin collector or dealer actually has. Have someone put some sort of numbered label on each coin, covering up the label if the coins are in containers (post-it-notes?), writes down which number is which grade. The numbers should be assigned by a dice roll or by getting numbers from the hotbits website. That person goes away with the list so as to make it a double-blind test. Then the person being tested tries to grade the coins, writing down the results. Compare the two lists, and it's a simple matter of statistics to find out that that person has, say, a 95% chance of being within 2 grades of the label. This is, of course the combined error of the testee and the original grader. Repeat for several coin collectors / dealers, and you will know that most coins are plus or minus N grades from what is on the label. Then publish it as an article in a cion magazine, inviting readers to repeat the test and send you the results. You could even find out which of you is the best and the worst at grading coins! My premise did not address the issue of "how well" anyone could grade, nor "how close" anyone could come to someone else's opinion on grade. It addressed the issue of the folks who claim that there is only one version of UNC. That they would be proven wrong seems intuitively obvious to all but the most casual observer. It matters not whether they could distinguish three versions, eleven versions, or a hundred versions. James |
#4
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The PNG survey was neither scientific nor valid in respect to grading
accuracy. It actually measured the personal preferences of the respondants and the market acceptance of brands of slabs rather than grading accuracy. The reason you will not see a scientifc grading study is because it would prove what everyone already knows - that there is no single grade everyone will assign to the same coin on any reliable basis. |
#5
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The test procedure you suggest would not be very scientific. Basically
you are confusing several different issues in measurement and grading. First is the concept that everyone's grading standards are the same. Although we all wish they were, we all also know that they are not. So, a coin that is graded MS 63 by one person and MS 67 by another may have been properly graded according to the standards of the individual graders. Before we can conduct any type of "scientific" analysis there has to be a uniform grading system that can be uniformly applied by all persons. As long as the concept of "market" grading is in place (where you are essentially grading the coin to what you think it is worth and not to its appearance of wear, strike, luster, etc) uniform grading will never exist. Second, you are confusing the statistical, and scientific, concepts of accuracy and precision. Accuracy is how close a measuring system comes to the "true" value. Because of the problems with the market grading system I doubt that we can ever assess grading accuracy (averaging several grading attempts is not a way to assess the "true" grade -- see my earlier posting on this topic or my editorial in Coin World). Precision is how close a measuring system produces the same value each time it is used. You can be very precise (same value each time) while being very innaccurate (way off the true value). Similarly, you can be very accurate (one measurement hits the true value dead on) but very imprecise (not able to acheive the same value each time). Since we all know that we cannot impose the same grading standards on all slabbers and collectors, it is pretty useless to try. We can, however, assess the precision of each grading company. Accumulate a bunch of coins and send them to a grading company. Get the results, crack them out of their slabs and send the into the same company again. Do this three or four times. Eventually you will get a reasonable assessment of how precise that grading company is in applying their own standards. Now do the same thing for another company. With the results for both companies in hand you could make a statement that one company is more, or less, precise in its grading standards than onther. You may even find that precision will vary as to coin type (ANACS claims to be the dollar experts in their ads -- maybe they are, in which case ANACS would have the highest precision for grading dollar coins, although perhaps a lower precision for other denominations). Thomas Greiner |
#6
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The test procedure you suggest would not be very scientific. Basically
you are confusing several different issues in measurement and grading. First is the concept that everyone's grading standards are the same. Although we all wish they were, we all also know that they are not. So, a coin that is graded MS 63 by one person and MS 67 by another may have been properly graded according to the standards of the individual graders. Before we can conduct any type of "scientific" analysis there has to be a uniform grading system that can be uniformly applied by all persons. As long as the concept of "market" grading is in place (where you are essentially grading the coin to what you think it is worth and not to its appearance of wear, strike, luster, etc) uniform grading will never exist. Second, you are confusing the statistical, and scientific, concepts of accuracy and precision. Accuracy is how close a measuring system comes to the "true" value. Because of the problems with the market grading system I doubt that we can ever assess grading accuracy (averaging several grading attempts is not a way to assess the "true" grade -- see my earlier posting on this topic or my editorial in Coin World). Precision is how close a measuring system produces the same value each time it is used. You can be very precise (same value each time) while being very innaccurate (way off the true value). Similarly, you can be very accurate (one measurement hits the true value dead on) but very imprecise (not able to acheive the same value each time). Since we all know that we cannot impose the same grading standards on all slabbers and collectors, it is pretty useless to try. We can, however, assess the precision of each grading company. Accumulate a bunch of coins and send them to a grading company. Get the results, crack them out of their slabs and send the into the same company again. Do this three or four times. Eventually you will get a reasonable assessment of how precise that grading company is in applying their own standards. Now do the same thing for another company. With the results for both companies in hand you could make a statement that one company is more, or less, precise in its grading standards than onther. You may even find that precision will vary as to coin type (ANACS claims to be the dollar experts in their ads -- maybe they are, in which case ANACS would have the highest precision for grading dollar coins, although perhaps a lower precision for other denominations). Thomas Greiner |
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