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#1
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Half grade mathematics
Posted By: Ken W.
David, |
#2
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Half grade mathematics
Posted By: Eric Brehm
No card is in 'perfect' condition, so perfection is just an abstract ideal that is used as a point of departure for assigning a grade. Defects which reduce the grade include those introduced at the time of manufacture, and those related to handling after a card enters circulation. Defects introduced at time of manufacture include uneven borders, out of focus image, and printing anomalies such as stray dots or blemishes, etc. Defects related to handling (or just age) include corner and edge wear, chipping, tobacco or wax residue, surface scuffing, color fading, discoloration of borders, scratches, creases, stains, ink and pencil marks, paper loss, tears and pinholes, and so on. |
#3
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Half grade mathematics
Posted By: davidcycleback
Ken, I meant if PSA could know exactly where .5 was (no margin of error), rather than rounding to nearest available number. |
#4
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Half grade mathematics
Posted By: Eric Brehm
Of course it is legitimate for a set to have a rating of 6.23, just like it is legitimate for the average height of a group of 20 men to be 5 feet 10.5 inches, even though no one guy has that actual height. |
#5
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Half grade mathematics
Posted By: davidcycleback
"There is really no mathematical meaning to it. A 10 is not 10 times better than a 1" |
#6
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Half grade mathematics
Posted By: Eric Brehm
You are correct, given that you have two cards in your set that have the same scarcity weight, you will get the same number of total points for a 10 and a 1, as you will for two 5.5's. But the fact is, in either case the average quality of your set is 5.5. Is having a 10 and a 1 better than having two 5.5's? Perhaps it is, certainly it more expensive, but your grade point average of 5.5 does give a good indication in either case of the average quality you've got. (Yes I know, you can drown in a lake of average depth 5 inches; that is the problem with averages.) |
#7
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Half grade mathematics
Posted By: steve
For example, take an "old" PSA 7 graded card. In order for it to get the 7 it had to range between 6.5 and 7.5 in the graders opinion. Less than a 6.5 it would be in a 6 holder, greater than 7.5 it would be in an 8 holder. |
#8
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Half grade mathematics
Posted By: BcD
The parent department of PSA,PCGS (coins) already breaks grades down to the .001's! |
#9
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Half grade mathematics
Posted By: Anonymous
Incorrect. According to all statements from PSA, a 6.99 (if they could grade so precisely) would be called a 6 because it did not meet the minimum requirements for a 7. |
#10
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Half grade mathematics
Posted By: davidcycleback
PSA said a 6.5 means the card is an extra good example of a six. A .5 essentially means a '+.' They could have just as easily used a .4, a .3 or a + to mean the same thing. So the .5 isn't intended as an exact mathematical measurement, but a notation that card is a premium example for that grade. PSA's numeration system isn't something you'd want to use to perform actual mathematical calculation with. |
#11
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Half grade mathematics
Posted By: Scot Reader
PSA is only bumping about 3-5% of cards submitted under the half-grade service. Moreover, most collectors are only re-submitting cards they think are particularly strong for the grade. Given the rigor of the half-grade standard, cards receiving a "point-five" grade cannot be thought of as simply at the midpoint between two integral grades. The PSA half-grade is better thought of as a qualitative, aesthetic metric without an exacting quantitative basis. |
#12
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Half grade mathematics
Posted By: Eric Brehm
I agree with Scot; as I said before, card grade numbers should be viewed only as labels for subjective condition qualities, not as literal numbers to be manipulated in a traditional mathematical sense. |
#13
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Half grade mathematics
Posted By: JimB
I have always assumed since Day 1 with PSA that a PSA 6 was everything in the 6.0-6.99 range. A PSA 7 was everything in the 7.0-7.99 range, etc. That is the impression I got from reading their grading criteria. I never presumed that a "6.6" would get a 7. |
#14
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Half grade mathematics
Posted By: Eric Brehm
JimB -- correct, that is why I explained in my earlier post that you start with the abstract ideal of condition 'perfection' and then work downward through the scale, dropping one whole grade (and now half grade) with the number of defects of various types you discover on close inspection. As soon as you discover the slightest thing that gets you out of the 7 range, even if in theory you have '6.99 quality', you drop to the 6 range. But maybe now you'll get a 6.5 instead of a 6. |
#15
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Half grade mathematics
Posted By: davidcycleback
I think the creation and application of a professional grading number scale for trading cards is one part applied mathematics and one part voodoo. And the third part is marketing. |
#16
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Half grade mathematics
Posted By: Eric Brehm
It is marketing driven by (or obfuscated by) voodoo mathematics. |
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