"What is the percentage change for a +1?" Topic
8 Posts
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| Windward | 20 Feb 2009 1:27 p.m. PST |
Hi My math skills are failing here, if I add a +1 to 2d6 what is the percent change of numbers occurring? I understand its a bell curve, so the percent chance of a 2 goes from 1/36 to 0, and a 12 goes from 1/36 to 2/36. I come up with roughly 9% is that correct? What if I add a +1 to 2d10? |
| Farstar | 20 Feb 2009 1:29 p.m. PST |
The percentage change is not constant, but is dependent on the target number. This is the fundamental difference between bell curve mechanics (multiple dice added together) and flat distribution mechanics (single dice). |
 BAMeyer  | 20 Feb 2009 2:00 p.m. PST |
Chances of rolling a number using 2d6 +1 compared to 2D6 3 -50.00%
4 -33.33%
5 -25.00%
6 -20.00%
7 -16.67%
8 +20.00%
9 +25.00%
10 +33.33%
11 +50.00%
12 +100.00% |
| Billiam | 20 Feb 2009 2:50 p.m. PST |
distribution 2d6 (rounded)
2 (3%), 3 (6%), 4 (8%), 5 (11%), 6 (14%), 7 (17%), 8 (14%), 9 (11%), 10 (8%), 11 (6%), 12 (3%) distribution 2d6+1 (rounded, assumes max. 12)
2 (0%), 3 (3%), 4 (6%), 5 (8%), 6 (11%), 7 (14%), 8 (17%), 9 (14%), 10 (11%), 11 (8%), 12+ (8%) % difference, 2d6 to 2d6+1 (same assumptions)
2 (-100%), 3 (-50%), 4 (-33%), 5 (-25%), 6 (-20%), 7 (-17%), 8 (+20%), 9 (+25%), 10 (+33%), 11 (+50%), 12+ (+200%) average change is +8% |
| Billiam | 20 Feb 2009 3:19 p.m. PST |
And because I'm bored, chance of x or greater: 2d6 (same assumptions)
2+ (100%), 3+ (97%), 4+ (92%), 5+ (83%), 6+ (72%), 7+ (58%), 8+ (42%), 9+ (28%), 10+ (17%), 11+ (8%), 12+ (3%) distribution 2d6+1
2+ (100%), 3+ (100%), 4+ (97%), 5+ (92%), 6+ (83%), 7+ (72%), 8+ (58%), 9+ (42%), 10+ (28%), 11+ (17%), 12+ (8%) % difference, 2d6 to 2d6+1 (same assumptions)
2+ (0%), 3+ (3%), 4+ (6%), 5+ (10%), 6+ (15%), 7+ (24%), 8+ (40%), 9+ (50%), 10+ (67%), 11+ (100%), 12+ (200%) average change is +47% (comparative) |
| tjantzen | 21 Feb 2009 2:19 a.m. PST |
Here is a small fun program for calculating dice roll probability of all kinds of dice and various modifying scenarios link regards
Thomas |
| pphalen | 22 Feb 2009 11:08 a.m. PST |
Others have answered, but from my perspective, all it does is skew the distribution so that the average expected value is now 8, versus 7. For 7 and below, the probability of each possibility drops by about 3% and for each one above 7 it increases by about 3% (so an occurrence of a 7 has a probablility of 16.7% for 2d6 and 13.9% for 2d6+1) Note that this is the absolute (point)change, not the percentage change (since I'm not a big fan of taking percentages of percentages…) |
| wballard | 17 Apr 2009 10:46 p.m. PST |
"Others have answered, but from my perspective, all it does is skew the distribution so that the average expected value is now 8, versus 7." Pedantic mode on: Yes it shifts the distribution value, no it does not 'skew' anything. Skew would change the shape of a distribution.
Pedantic mode off. |
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