Does it really matter if dice are randomized?

Question

I was playing MTG with some friends the other day, when a guy walks up and challenges me to a game. He insisted that he would not roll my spin-down die to determine who goes first. When I pointed out that it doesn't matter, because probabilistically, each side should have a 1/20 chance of showing regardless of the order of the sides, he assured me that there exists a "technique" by which someone could throw an ordered dice such that he has a higher chance to win a dice roll.

Paranoia aside, does anyone know if such a technique exists? Is there any documentation on such a technique?

Answer 1

As I noted in a comment, there are techniques I've seen people use with spindown dice - most notably a sort of 'skitter along the table' throw where the die is primarily slid rather than tumbled - that can be used to great effect in rolling high numbers. There's enough imprecision that shots can't really be called precisely, but for spindown dice where all of the faces around a high-numbered face are also high-numbered, they lead to significantly biased rolls.

You might ask why it matters, since both players are rolling the same die and both have access to the same technique - but the point is that there's an ethical asymmetry; one player is (presumably) trying to roll the die in a 'fair' fashion with an unbiased roll, either out of a sense of internal fairness or because they have no reason to suspect the other player is cheating them. Meanwhile the shark is (also presumably) well aware of the skew in the game and willing to use that skew to their advantage.

For what it's worth, I don't believe most people rolling spindown dice do it with any intention to cheat; the life counter is just what they have handy, and so it's a natural choice. But there are people who will use it for that purpose, and so anyone who isn't willing to is at a slight overall disadvantage. Most of the time, at an FNM or in a casual game like the one you describe, it just doesn't matter; who cares if you're an underdog in a die roll that has a maybe 5% affect on the outcome of a game that's just for fun? But there are certainly circumstances where it does matter, and some people just get in the habit of caring about every little thing so that they build the mental rigor for when it does matter.

As for myself, I usually don't care, though at something like a PTQ I'll insist on a more effective means of randomization. My preferred choice is either to flip a coin with a call in the air (which is about as close to 'I cut, you choose' as a randomization method gets) or to toss about 5d6; they're quick enough to count, and hard enough to really skew that I can trust in the results.

Answer 2

As of the July 2021 Magic Tournament Rules Release Notes, spindowns are prohibited from being used as a randomized die at Competitive REL (though are seemingly being okay in casual play):

Spindown life trackers are prohibited. We're not going to worry about it in casual play, but at Competitive REL, we expect the numbers to be distributed appropriately to reduce any potential for manipulating dice rolls. How easy they are to manipulate is a matter of debate, but with the wide array of other randomization methods available, keeping them out removes any potential appearance of impropriety.

This section isn't updated on the Magic Judge website, but the full Magic Tournament Rules document can be downloaded here.

Answer 3

If 20 and 2 are next to each other, adding a weight to the opposite side of the dice would increase the chances of a both 20 and 2 getting rolled.

If 20 and 19 are next to each other, adding a weight to the opposite side of the dice would increase the chances of rolling a high number.

In other words, it's easier to make a trick dice if it's a countdown dice. This matters if only one person uses the trick dice, but it sounds like this isn't the case here.

Answer 4

Certainly there are tricks to rolling dice, but I believe all but one of them apply to a D6 at best. The more numbers your die shows, the harder any trick becomes, because a D20 topples much more easier than a D6, because its ratio of weight per single face area is much larger than for a D6, and the angles between faces are much larger than 90°. Compared to a D6, a D20 is practically a ball. A D20 simply cannot hold virtually ANY momentum with a single face, unlike a D6.

Try painting a small spot on a marble and make it land on exactly that spot. There is pretty much only 1 somewhat reliable way to do it: Spinning the marble on the spot and hoping that it doesn't spin out of control in the end. That's the only trick I can imagine could work for a D20. Fortunately, that trick is trivial to spot, so as long as someone does a normal rolling motion, a D20 should be safe from manipulation.

All that is assuming fair dice - if someone wants to retreat to the position that your die is physically manipulated, you can't disprove that any way short of cutting up your die.

Answer 5

Spindown counters are not rated for use as 20-sided dice and can't be used as such... use a random method to decide who goes first.

Answer 6

This controlled die rolling stuff is just nonsense... its simply a meaningless factoid that ego-inflated magic players use on each other to try and build themselves up before a game.

Yes, spindown dice do not have evenly distributed numbers, but if you are telling me someone can casually pick one up and control their roll to be better than mine then you are delirious. To achieve this you'd have to pick up the die, find the high/low side, and then carefully roll/drop it to get the desired result. By this time you are looking at the guy like "are you kidding me man... you are trying to cheat the roll!"

People will relish the rare attempts they get to demand the 2d6 roll, and they will spout this reason every time with a proud smile on their face, now sure that they know all the ins and out of magic better than you do.

I suggest you smirk to yourself at what a tool they are and roll whatever they want... then crush them in the game!