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.
2 Answers
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.
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 Dec 18, 2012 at 3:07
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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.– corsiKaFeb 13, 2013 at 18:37
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@SevenSidedDie If you want a bell curve approximation, just take a hundred dice instead of two.– Joe Z.Feb 26, 2013 at 16:29
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2@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. Feb 26, 2013 at 17:57
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