The Top 10% Ability Scores

seasong

First Post
On a 3d6 distribution, what is the top 10% of the population, and how can I ensure that the PCs are in it?

(This assumes you want your PCs in the top 10%; the 4d6/drop lowest actually ensures that some of them will be)

This question was driving me batty. The reason is simple: 3d6, over six ability scores, has slightly over 100 trillion possibilities. Even if you boil it down to 3-18, there are over 16 million possibilities. Spreadsheets aren't meant for that kind of abuse, and I'm not enough of a mathematician to sit down and start calculating the probabilities of each die result. So I abused a spreadsheet. I've attached it, in case anyone cares enough, but it's really just a notepad.

I also had to define what I meant by "Top 10%". I went with two possible definitions:

1) Add up your ability scores. The top 10% of that total.
2) Add up the point buy COST of your ability scores. The top 10% of that cost.

On point 2, I went with this extrapolated cost chart:

3: -14
4: -10
5: -7
6: -4
7: -2
8: 0
9: 1
10: 2
11: 3
12: 4
13: 5
14: 6
15: 8
16: 10
17: 13
18: 16

In both cases, I ended up rounding a bit to the top 11%, in order to have a clear markoff.

SUM: If the sum is 80 or more, you are in the top 11%.
COST: If the cost is 36 points or more, you are in the top 11%.

So that leaves a few methods for calculating PC ability scores, if you want your characters to be in the top 11% on a 3d6 distribution:

a) Roll 1d6+12 for all ability scores.
b) Give 80 to 108 points to divide among the scores at a 1:1 ratio. Note that 98 points or more is "1 in 25 million" territory, and 94 points is around "1 in a million" territory.
c) Use the DMG point buy, with 36 to 96 points. Note that 70 points or more is "1 in 100 million" territory, and that even 60 points is "1 in a million" territory.

I like the 90 points (1:1 ratio), as it goes to about 1 in 50,000 territory (or roughly the top 0.002%), but still allows one or two reasonably low scores.

Well, anyway, that's my waste of mental space for the week :).
 

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seasong said:
This question was driving me batty. The reason is simple: 3d6, over six ability scores, has slightly over 100 trillion possibilities. Even if you boil it down to 3-18, there are over 16 million possibilities. Spreadsheets aren't meant for that kind of abuse, and I'm not enough of a mathematician to sit down and start calculating the probabilities of each die result.

Did you know that Excel has just enough room for each possibility? 256 columns by 65536 rows = 16777216, exactly the same number as the number of stat combinations 3-18 for 6 scores. Of course, that would get pretty cramped...
 


Uh, Seasong, are you certain? My community builder program says the top 10% is starkly at 72 points for #1 there. The results are completely consistant - I make a million people, over 100,000 of them have 72 or more attribute points total.

Or ~25 point buy. Or average results on straight 4d6. The math was done for this, I suspect.

80 points is the top 1%. This also is pretty consistent.

85 points is the top .1%.

89 points is top .01%

Beyond that I don't generate enough people to be absolutely certain, I think 96 points is 1 in 10 million.
 
Last edited:

I just finished a complete analysis (that is, mapping all 101,560,000,000,000 or so points). I used a few tricks to make it calculatable, but didn't resort to anything banal like Monte Carlo.

26 points is sufficient to put a person in the top 90.3%.

I have the exact* numbers on a spreadsheet if anyone wants it.

* Some of the numbers really aren't exact; Excel only calculates 11 decimal places, so numbers > 10^11 are rounded (but very close)
 

More analysis*:

78 points is 1:1,000,000,000
74 points is 1:100,000,000
69 points is 1:10,000,000
65 points is 1:1,000,000
58 points is 1:100,000
52 points is 1:10,000
45 points is 1:1,000
37 points is 1:100
26 points is 1:10
0 points is 10:1
-13 points is 100:1
-23 points is 1,000:1
-31 points is 10,000:1
-39 points is 100,000:1
-44 points is 1,000,000:1

* Rounding to higher point total for 1:x and lower for x:1.
 

Note that my values are one for one rather than point buy, since that's how my program sorted it.

I think 92 points on 1:1 is 1 in 100,000, and 94 is one in a million.
 


CRGreathouse: Could you post your spreadsheet? Or e-mail it to me at "seasong at texas dot net", either one. I'd love to see it :D.
 

I was under the impresstion that the number of possibilities was:
Variation^times done or V^T(coins try it)
So 6 variations and it's done 3 times so that 6^3 which 216, 216 variations done 6 times, 216^6=
101,559,956,668,416 possibilities which is 101 trillion?
 

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