Guidelines for Generating a 2D Results Tables

[CRMcNeill]

The probability of a particular number coming up on a roll of 2D changes from number to number, with the numerical odds as follows:

2 = 1/36
3 = 2/36
4 = 3/36
5 = 4/36
6 = 5/36
7 = 6/36
8 = 5/36
9 = 4/36
10 = 3/36
11 = 2/36
12 = 1/36

So, for example, whenever you roll 2D, the statistically most likely result is a 7 (a 6-in-36 chance, or 1-in-6) while the statistically least likely result is either a 2 or a 12 (each with a 1-in-36 chance).

When generating a list, you can play with the numbers, so as to make a given result more likely. For example, if you wanted to have two results of equal likelihood on a 2D roll, you would assign one to the 2-3 result, and the other to 4, giving both a statistical likelihood of 3/36 by adding the odds of a given set of numbers together to create a greater likelihood than either would generate on their own (3/36 = 1/36 + 2/36).

For example, on a 2D Table I posted earlier, I used the following:

2 = 1/36
3 = 2/36
4-5 = 7/36 (3/36 + 4/36)
6-9 = 20/36 (5/36 + 6/36 + 5/36 + 4/36)
10-11 = 5/36 (3/36 + 2/36)
12 = 1/36

Essentially, by treating the probability numbers as fractions, adding the numerators of a multi-number set will give you an idea how likely a given result is, and help you structure your lists to make a particular result the most likely outcome.

Enjoy.
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"No set of rules can cover every situation. It's expected that you will make up new rules to suit the needs of your game." - The Star Wars Roleplaying Game, 2R&E, pg. 69, WEG, 1996.

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