Question about Dice.

[Pikarya]

So I'm wondering. Can using two dice that don't have the same pips/number placement mess with probability, or cause unintentional cheating?

Reason why I ask. I recently purchased two pairs of dice that were custom made.

The pips on the dice are not in the exact same locations, its almost as if the pair is "mirrored".

Here's what I mean.

http://i53.tinypic.com/2aiputx.jpg

Smallest dice is a normal pair from the store.
Top 2 are the customs.

[Kerberoz]

Enough to cause a discrepancy across millions of rolls? Probably. Enough to cheat? No.

If you want to make loaded dice, bake them at a low temperature with the "good" numbers up. It melts the interior a bit towards the bottom.

[SephYuyX]

Highly doubtful. The force applied to them as you release them from your hand is much more than the (very very very little) weight differences on each side.

[Cantih]

Also, different dice designs often REQUIRE changes to things like pip location, depth, etc. to keep the die balanced.

[Pikarya]

Like I understand flat (casino dice). Since these are rounded (I think backgammon styled) they roll more forward (which is illegal in casinos anyways).

But yeah, didn't know if it was anything to worry about. Spent the last two days trying to research unmatched pair dice and their rates of probability and found nothing.

edit: Also these are for tabletop gaming if anyone was wondering.

[Eratosthenes]

I wouldn't expect a mirror image to mess with any probabilities, but that one with two fours on it definitely will.

[Cantih]

I doubt there would be anything on it.
A die is a die, it's random or loaded.

A loaded die mixed in with a normal die will, if you're summing the results like craps, alter the average range of the result.
If you're rolling dice for successes (as in Shadowrun, or White Wolf games), will alter the number of successes you get.
There really isn't anything TO research, aside from how subtle you can push cheating before anyone notices and the FFXI mathology of "cost/effective ratio" to bothering.

The thing to look into is IF the die is actually non-random, or, how custom patterns alter the randomness, if the custom dice manufacturers actually test their dice, or use physics and spatial formulas in the design of the die. Or they just smack a custom 1-6-w/e number instead of a pip, mark a premium, and put it out there.

If you're really concerned, find dice that have painted/stained faces instead of drilled/engraved ones.

[Cantih]

I wouldn't expect a mirror image to mess with any probabilities, but that one with two fours on it definitely will.

The circled four is either a one or a six.
It's the symbol for the Fantastic Four, the X on the black dice is X-Men.
He got these for a superhero P&P RPG is my guess.

[Pikarya]

Logo's = 6, and yes RPG.

[Mr. Flippy]

sometimes the weight differential will cause some imbalance causing some higher odds in roll outcomes. i helped Pikarya test the dice and for some reason they are rolling extremly well. only 3 rolls out of like 40 or so came up lower than a 3.

[Kaylia]

What are the odds of getting a particular number on the first dice? 1/6
What are the odds of getting a particular number on the second dice? 1/6

If they are fixed...then yeah, but that's not really the question.

[Elesirdur]

Short answer, no the physical properties of the die won't throw off the probability in the short run.

This article might give you some insight into some common probability and statistics fallacies: tvtropes: You Fail Statistics Forever. Be wary though, it is tvtropes and it will ruin your life.

[Talus]

Probabilities are:

2: 1/36
3: 2/36
4: 3/36
5: 4/36
6: 5/36
7: 6/36
8: 5/36
9: 4/36
10: 3/36
11: 2/36
12: 1/36

If the dice are truly balanced, over time your rolls should resemble the given probabilities, regardless of the pip placement (again, if the dice are balanced). As other posters mention, each die has a probability of 1 in 6 for each side, since it's 6-sided. To find the probabilities for 2 events like dice you use the multiplicative rule, i.e. 1/6 x 1/6 for rolling snake eyes is 1 in 36 like above (and rolling a 3 is possible with a 1 or 2 on both dice, and a 1 or 2 on the other, so that is (1/6+1/6)x1/6 either way).