4 ms·

Wouldn't a better experiment be to roll one 10K times and see if the sides have equal probability? Who cares if the dimensions are a little off if the effect on

Wouldn't a better experiment be to roll one 10K times and see if the sides have equal probability? Who cares if the dimensions are a little off if the effect on the roll is minimal, or conversely are even the best toleranced dice still biased?

bikamonki 5y ago
https://hackaday.com/2019/06/20/automated-dice-tester-uses-machine-vision-to-ensure-a-fair-game/ https://hackaday.com/2019/06/20/automated-dice-tester-uses-m...
- mwcremer 5y ago
  And if you read that report, you see: "Gamescience dice are more consistent than the X-Wing dice", with some analysis regarding the flashing from the mold suggesting that sanding it smooth will increase the consistency.
  - YeGoblynQueenne 5y ago
    That's true for d8 used in X-Wing. The report linked from the hackaday article links to a report from awesomedice.com that tested d20s: https://www.awesomedice.com/blogs/news/d20-dice-randomness-test-chessex-vs-gamescience https://www.awesomedice.com/blogs/news/d20-dice-randomness-t... They _manually_ tested Chessex and Gamescience dice by rolling them thousands of time. They found both brands' dice to be off. Gamescience dice had a big dip on the number 14 face, which is the face that has the bit of flash where the die is cut off the sprue by hand. I suspect it's just easier to make a fair d8 than a fair d20. That probably goes for other die sizes also. I was looking for a d14, d16 and d18 and while I found the first two from Gamescience, I could find a d18 only from one brand, other than Gamescience, so I'm guessing that Gamescience decided they simply couldn't make a fair d18 work. I mean, why skip d18 when you have d14, d16 and d20?
jedimastert 5y ago
Fun fact: Die don't have to be the same all sides to be provably fair. Check out the "skew die" https://www.mathartfun.com/DiceLabDice.html https://www.mathartfun.com/DiceLabDice.html And a video https://www.youtube.com/watch?v=uAnCL3vhVIs https://www.youtube.com/watch?v=uAnCL3vhVIs
- loonster 5y ago
  Those dice look to have either the same face or a symmetrically opposite face. It would be more impressive to see a die with a pattern of a buckyball with the pentagons and hexagons having equal probability of being rolled. I'm sure its theoretically possible, just not practical.
  - unholiness 5y ago
    If the faces are different shapes, their probability would depend on how you quickly you roll them.
- vikingerik 5y ago
  The dice on that page are in fact the same on all sides. For each of those dice, every face on it is the same as every other face, the same shape and attached to the same adjoining faces at the same angles. They're not regular - the faces are not regular polygons - but that's not a requirement to have an equal chance of landing on each side. The standard d10 is an example of this in itself.
  - unholiness 5y ago
    I think he means the same distance between opposite faces, the quantity that was discussed in the article. The skew dice faces are all identical but none are even parallel.
    - vikingerik 5y ago
      Parallel opposite faces isn't a requirement for fairness either. A standard d4 doesn't have that.
funstuff007 5y ago
Ludology showed that for Pop-O-Matic any individual roll was random, but roll n and roll n+1 were not random. The number on the opposite side of the side of roll n, had a much higher than 1/6 chance for roll n+1. https://ludology.libsyn.com/gametek-2755-pop-o-matic https://ludology.libsyn.com/gametek-2755-pop-o-matic

bikamonki 5y ago

https://hackaday.com/2019/06/20/automated-dice-tester-uses-machine-vision-to-ensure-a-fair-game/ https://hackaday.com/2019/06/20/automated-dice-tester-uses-m...

mwcremer 5y ago
And if you read that report, you see: "Gamescience dice are more consistent than the X-Wing dice", with some analysis regarding the flashing from the mold suggesting that sanding it smooth will increase the consistency.
- YeGoblynQueenne 5y ago
  That's true for d8 used in X-Wing. The report linked from the hackaday article links to a report from awesomedice.com that tested d20s: https://www.awesomedice.com/blogs/news/d20-dice-randomness-test-chessex-vs-gamescience https://www.awesomedice.com/blogs/news/d20-dice-randomness-t... They _manually_ tested Chessex and Gamescience dice by rolling them thousands of time. They found both brands' dice to be off. Gamescience dice had a big dip on the number 14 face, which is the face that has the bit of flash where the die is cut off the sprue by hand. I suspect it's just easier to make a fair d8 than a fair d20. That probably goes for other die sizes also. I was looking for a d14, d16 and d18 and while I found the first two from Gamescience, I could find a d18 only from one brand, other than Gamescience, so I'm guessing that Gamescience decided they simply couldn't make a fair d18 work. I mean, why skip d18 when you have d14, d16 and d20?

jedimastert 5y ago

Fun fact: Die don't have to be the same all sides to be provably fair. Check out the "skew die" https://www.mathartfun.com/DiceLabDice.html https://www.mathartfun.com/DiceLabDice.html And a video https://www.youtube.com/watch?v=uAnCL3vhVIs https://www.youtube.com/watch?v=uAnCL3vhVIs

loonster 5y ago
Those dice look to have either the same face or a symmetrically opposite face. It would be more impressive to see a die with a pattern of a buckyball with the pentagons and hexagons having equal probability of being rolled. I'm sure its theoretically possible, just not practical.
- unholiness 5y ago
  If the faces are different shapes, their probability would depend on how you quickly you roll them.
vikingerik 5y ago
The dice on that page are in fact the same on all sides. For each of those dice, every face on it is the same as every other face, the same shape and attached to the same adjoining faces at the same angles. They're not regular - the faces are not regular polygons - but that's not a requirement to have an equal chance of landing on each side. The standard d10 is an example of this in itself.
- unholiness 5y ago
  I think he means the same distance between opposite faces, the quantity that was discussed in the article. The skew dice faces are all identical but none are even parallel.
  - vikingerik 5y ago
    Parallel opposite faces isn't a requirement for fairness either. A standard d4 doesn't have that.

funstuff007 5y ago

Ludology showed that for Pop-O-Matic any individual roll was random, but roll n and roll n+1 were not random. The number on the opposite side of the side of roll n, had a much higher than 1/6 chance for roll n+1. https://ludology.libsyn.com/gametek-2755-pop-o-matic https://ludology.libsyn.com/gametek-2755-pop-o-matic