My weekend D&D group has a different way of rolling attributes for characters, and it’s probability has been bothering me mathematically for a couple of weeks now. First, I should show how the regular rolls work for comparison.
Normally when you create a D&D character, you roll 3 six-sided dice (also known as 3d6) and add them up to get a total. You do this 6 times and apply each totaled value to one of six character attributes.
A higher character attribute is better. 10 is average, while 18 is the best you can roll. Anything below a 9 is below-average for a human, so a character with an intelligence of 6 isn’t so great.
The numbers in each attribute are used to determine attribute bonuses. Attribute bonuses are used inthe game to affect certain skills. For example, a character with an Intelligence rating of 18 receives a bonus of +4 to all skills related to intelligence. A character with a Strength of 18 receives a bonus of +4 to all melee attacks and to damage. This factors into the game significantly.
For every two points in an attribute, the bonus changes by one. A single bonus point is an effective 5% bump in chance to succeed. So a character with a Strength of 18 has a 5% better chance of hitting a creature than a character with a Strength of 16, and the stronger character also does at least one more point of damage when he hits.
Ok, so now I will describe our in-house rolling system, and you can see how horribly broken it is.