Friday, February 7, 2014

Testing d6′s

After seeing this article about d6's being biased to roll ones, I thought it was time to do some more dice testing of my own. Here's what I came up with.

What is being tested?

Are some types of six-sided dice biased? If so, what kind of dice are the best ones to roll up your character with?

Test Conditions-

Three d6's of the same type are rolled together in a dice cup onto a hard wood table- 48 times. Perfect results would be that each face on the dice would appear 24 times. For this test, the Sum Squared Error (SSE) must be 264 or less for the dice to be considered to be fair. (All I know about testing dice is from this great article at Delta's D&D Hotspot.) The closer the SSE is to 0, the more fair the dice are.

The Dice Tested-
  • 10mm d6's - square edges with pips. I got these from some game maybe from Awful Green Things from Outer Space.
  • 12mm d6's - rounded edges with pips. The most popular kind of d6's used by gamers.
  • 14mm d6's - rounded edges with numbers. The kind of dice that usually come with D&D boxed sets.
  • 16mm d6's - square edges with pips. The big d6's of the kind you see in Walmart.
  • GameScience d6's- square edges with numbers.


3d6 Average Rolls (best to worst):
  • 11.02 - 10mm
  • 10.81 - 16mm
  • 10.69 - 14mm
  • 10.58 - 12mm
  • 10.19 - GameScience

Fairness (SSE, best to worst):
  • 28 - 14mm
  • 82 - 16mm
  • 144 - 12mm
  • 152 - 10mm
  • 210 - GameScience


The results were surprising as the GameScience dice finished last in both fairness and high rolling. The 12mm dice that are so impugned in the article mentioned above are shown to be reasonably fair and I now suspect that article to be complete bs. Also surprising is that the lame dice that came in basic sets are actually the fairest rollers. But the most important thing learned here is that I'm going to start using those 10mm dice to roll up my characters from now on.