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H C
United States
Philadelphia
Pennsylvania
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I'm not very good at math and don't trust myself. Also what repercussions are there to replacing a D20 system with a 5D4 system?

I was thinking it'd be a lot more stable but may be less exciting...anyone try?
 
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Chris Geggus
United Kingdom
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I won't even attempt the maths, but the one obvious difference will be the loss of numbers 1 to 4. You would change a chance of 1 - 20, to a shot at 5 - 20. Not sure that really would be construed as more stable.
 
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Ryan Byrd
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Griffin
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anydice.com is your friend.

http://anydice.com/program/89b

For this case, the chance of a 5 (minimum roll) is way less than the minimum for a d20. The chance at 20 is also way less.

There is always a bell curve created when you roll multiple dice, meaning the median values will always have a more likely chance of appearing.
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James Hamilton
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Stockport
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You will end up with a range from 5 to 20 rather than 1 to 20.

There will be a 1 in 1024 chance of a result of 5 or 20
a 5 in 1024 chance of a 6 or 19
15 in 1024 of a 7 or 18
35 in 1024 of 8 or 17
65 in 1024 of 9 or 16
101 in 1024 of 10 or 15
135 in 1024 of 11 or 14
155 in 1024 of 12 or 13

So more than half the time you will get a result in the range 11 to 14
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Dave Lartigue
United States
Springfield
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A d20 gives the exact same chance of rolling any number. It's a completely flat curve, with all results having a .05 chance of happening. 5d4 gives you a distribution curve, with the low and high results - 5 and 20 - being much less likely than the median results of 12 and 13.

Having to roll a 20 on a d20 sounds exciting, but it's no different from having to roll anything else. 20s aren't any more difficult to come by there. On a 5d4, you can only do it by rolling a 4 on all the dice -- a one in 4^5 chance (don't quote me there; my probability math skills are rusty).
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Mr. D
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Oneonta
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The chance of any particular number showing up on a d20 is equal. There is a 1/20 (5%) chance to roll a 20. Also, you can figure out the odds (rounded to 5% increments) that you want of a "successful roll" and set the appropriate target.

The chance of a particular number showing up on 5d4 will be on a bell curve. The odds of rolling a 12 or 13 will be MUCH higher than the chance of rolling a 20. In fact, the odds of rolling a 20 will be 1/1,024 (slightly less than 0.1%) Setting the odds of a "successful roll" can be much more precise, but will take a lot more math.
 
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