# 1d100 or 2d10?

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### #1 MalVeauX

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Posted 27 November 2013 - 06:35 PM

Heya,

I was wondering, I've never really looked into it, but I imagine there is a statistical significant difference between using a 1d100 and 2d10 for rolling a 0~100 number in this system. Both in real world and using computer based random generates for dice (rollers). I can't imagine they are really worlds apart in terms of the average they roll. But I do think they have to be different, because taking the average of a 1d10, twice, is quite different from a single 1d100 average.

I'm not looking for power play or using a rolling system to improve averages. Just looking into for the sake of interest.

Thoughts?

Very best,

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### #2 CaptainStabby

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Posted 27 November 2013 - 06:43 PM

Anydice.com might be able to do the math. Duno if it does percentile off hand tho.

Edited by CaptainStabby, 27 November 2013 - 06:56 PM.

### #3 Errant

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Posted 27 November 2013 - 07:26 PM

Assuming you're using it as percentile, the odds of getting a particular number are (1d10)*(1d10). Since there's only one combination for each number, this is a 1:100 chance of a particular number turning up.

### #4 Erathia

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Posted 27 November 2013 - 08:12 PM

Assuming all dice are fair, Errant is right. I'm inclined to think that because no die is perfect there's probably more bias using 2d10, but that's not a calculation I feel like doing right now.

For example, how do you roll a 42 with a d100? You get that one exact side out of 100 possibilities, or a 1% chance. Rolling it with a 2d10 requires you to roll a "40" on one SPECIFIC 10, and then a 2 on the other 10. There's a 10% chance of doing the first roll, and then assuming you succeed you have another 10% chance of rolling the 2, and 10% of 10% is 1%, so we're okay.

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