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Are there dice that have both positive and negative numbers, where the average result is zero? I'm imagining a die labeled something like: -2, -1, 0, +1, +2. I feel like I've seen dice like this, but I'm not sure what they'd be called or how to find them.

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2 Answers

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Probably the most commonly available ones are called Fudge dice, as used in the Fudge/FATE roleplaying games.

A Fudge die is a six-sided die with the following sides: minus, minus, blank, blank, plus, plus.

Games generally have players rolling a couple of Fudge dice together and adding them up, which creates a curved probability distribution centered around zero. 3dF, for example, gives you a range from -3 to +3, with 0 as the mean, median, and mode.

This Wikipedia article has more information.

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+1, but by "average, median and mean" did you mean "mean, median and mode"? – tttppp Jul 11 '12 at 8:48
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You could take any two normal dice of different colors and denote one as the positive die and one as the negative die.

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Yup. This gives a triangular distribution rather than a bell curve approximation, but it is quick, easy to find dice for, and is close enough that it's often suggested as a drop-in replacement (using d6s) for the harder-to-acquire four Fudge dice. +1 – SevenSidedDie Dec 18 '12 at 3:07
If you lack dice of different colors, you can just roll them both and flip a coin (heads positive, tails negative) or a third die (even positive, tails negative). A bit more of a pain, but considering the absurdly high number of plain Jane white dice floating around my house, it would be reasonable. – corsiKa Feb 13 at 18:37
@SevenSidedDie If you want a bell curve approximation, just take a hundred dice instead of two. – Joe Z. Feb 26 at 16:29
@JoeZeng 50d6 - 50d6 actually gets you a narrow bell with long flat tails—not a nice distribution at all. For a nice bell curve approximation you only need 2d6 - 2d6. Everyone knows that adding more dice gives a nicer bell when you're summing them, but that intuition absolutely does not hold when subtraction is involved. – SevenSidedDie Feb 26 at 17:57
Whoops. I forgot that about subtraction. – Joe Z. Feb 26 at 18:24
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