New Deck of DM Things Merch: deck-of-dm-things-merch.print... Thank you for watching! SEO Stuff: Types of D20s Dice DnD dice spindown d20 mtg dice Dungeons and Dragons Dice Explained
Long ago, it had been explained to me that the reason spin-down D20s weren’t generally permitted in events (at least for the events I was playing in/judging) had less to do with inherent flaws of the number distribution in an “honest” roll, but rather the potential of their pattern’s exploitability for those intending to exploit that distribution. It would be interesting to test how much one could exploit the pattern to manipulate results (or, realistically, if such exploitation is practically possible).
I used to do magic and I had a trick that relied on rolling a dice in a specific way so it would land how you wanted but looked like it rolled. This is much harder to do with a d20 however after some trying I can kind of manipulate it so with practice I could probably make it so I only roll high on a spin down. This is however a small test I did at home for only a few days.
Yeah if you're going for high numbers, it's significantly easier on a spin down. Roll it against a surface, make it bump, even just start it in a specific orientation and what was a 1/20 chance affected by skill becomes a 4/20 to get something good enough affected by skill much more heavily. Hell you don't even have to be doing it intentionally, I used to roll against a box all the time and we just threw it in a way where it hit the sides most rolls. On a d20 that barely matters, but a spin down would've stopped at a number within the cluster of whatever hit the side. Edit: also, the majority of spin downs aren't manufactured to be balanced, they don't need to be balanced they just display a number.
@@bye1551and how would you be able to choose which side of the dice hits the wall? Maybe I'm missing something in your comment, but if you just throw the dice it shouldn't matter if it hits the wall or the floor. Simply because you can't guarantee or even influence wich side hits.
Dices where the numbers are cut you can cut more material in the numbers you want so they roll with more frequency. How much it affects I don't know but it is enough that I have heard and seen this trick done.
@@Jehty_ oww yes you can by checking the die in your hand and making the right flick or the wrist you CAN influence this. Tried an tested. Takes a little bit of practice but the skill can be developed quickly
So, the thing with spindowns is, I think, if they're being rolled fairly, they're probably not really any less random than a standard D20; considering that the standard D20 manufacturing process includes, presumably, making sure the die is balanced well enough, you'd probably have to do it on purpose to make the die poorly balanced. However, because all of the high numbers are on one side and all the low numbers are on the other, it makes it much easier to manipulate the die into always giving you a number in that 16-20 range.
Testing a die for fairness would take more time than actually making the die. whether the dice are mass manufactured or small batch, that's just not worthwhile for the manufacturer. think about how hard-edge dice are often marketed as more fair due to the tumbling process of typical dice allegedly reducing the fairness of each individual die. If the makers of typical dice had the testing records for this, it would be very clear cut whether hard-edge dice are an improvement, and that kind of clarity is just not what we see. Followup: the video mentions a "float test". I was implicitly assuming a higher standard of testing (rolls and statistics) in the claim about testing time. With small batch manufacturing, float testing each die is at least achievable, though still not worthwhile in my opinion. float testing each die with mass manufacturing is still intractable though.
@@LaBlueSkuld They do a little bit. A very little bit. And pretty much only for transparent and translucent dice. I know this because I buy them by the bucket on Chinese websites. Sometimes they have bugs stuck inside of them. That's pretty cool. They also roll hilariously biased. But it's pretty much impossible to tell what exact number they're biased at without spending way too much time doing the math. It's funny watching people get angry at one set of dice to swap them for another set of dice, they also get angry at.
As the only person at my table who recognises a spindown vs a standard d20, I always balk at one of my players bringing a spindown to DnD. And then I immediately mentally talk myself down because there's no real impactful difference and my player just picked that die because they think it's pretty. Excellent video!
The way I've always understood it is that placing numbers so that opposites add to Dice Sides + 1 is an ancient measure intended to offset the fact that old dice weren't very precisely made, and to make it more difficult to 'weight' the dice. It might even go back to the use of knucklebone dice (aka Astragaloi, Talli, Shaggai) which had only four sides and were numbered 1, 3, 4, 6, with the numbers 1 and 6 being only 10% likely compared to the 3 and 4 being 40% likely. This required 1 and 6 to be opposite one another and 3, 4 likewise, because that's how the astragalus bone is shaped - opposite sides are roughly the same size and shape, meaning the die's average remained somewhere close to the middle of its range. These measures are no longer necessary with modern dice, which are much more uniformly shaped and weighted.
Having seen the rest of the video now, I think I'll also point out that simply being off-balance isn't enough to make a spin down die noticeably unfair, it specifically has to be unbalanced away from or towards the 'high point' (the centre point at which all the highest-rated facets are clustered around). As I noted above, the 'opposite sides' safety measure is only really effective at preventing deliberate cheating and correcting excessively poor manufacturing.
yeah, you're assuming that the imbalanced dice is something people don't want today, and is something that is all but eradicated. There are still cheaters around, plenty of them. They could be skill-based with sleight of hand, or have imbalanced dice on purpose. So why allow a die that allows for those by grouping all the good numbers on one side. It's real difficult to use sleight of hand or to imbalance a regular d20, since every good value (15+) is surrounded by bad values, and even the slightest miscalculation spoils the good result. But if all the good results are on one side, then with a miscalculation you just get a slightly worse result. Instead of a 20, you get a 17, stuff like that.
I have absolutely no idea how I got here. I don't even play DnD, or any another dice rolling game. I am though definitely pleased with the algorithm, but I am a wee bit alarmed it knows me so well. Now you've got me down the rabbit hole on dice sir! I've just been googling what a "float test" is!
You and I both, brother. Have you been watching Bauldr's Gate 3 content too? (a game I don't even own because turn based RPG's are icky and yucky but that one looks nominally interesting)
I’ve totally played DnD, but I’ve never worried that much about my dice as long as we’re all using the same ones…still. I was absolutely and totally fascinated by this.
Yes but that isn’t actually what this discussion is about. It’s about the complete randomness of a random role. How someone can manipulate their dice role is a different matter.
@@JackWest-sp1zc in the video, he mentioned spindown dice had been banned in some tournament settings, and the concern in those cases was almost certainly to avoid intentional manipulation rather than concern over deviation from being absolutely random. So yeah, that's not what the video was about, but it would have been good to discuss at least briefly. But he preferred to make a long video answering a question nobody asked. (Which I did find interesting anyway.)
@@JackWest-sp1zcit is what the video claims to be about because he introduces it with the fact that those dice are widely banned and that is the sole reason that they are banned.
I'm an applied cryptographer. Absolutely love these kinds of videos exploring practical real world rng scenarios. Your conclusions are correct, both in what you expected, and why you observed what you observed. To test a dice's balance by rolling, the number of rolls becomes basically impossible quickly. The more biased a dice, the fewer rolls you need to draw a conclusion, but even quite biased dice can be basically indistinguishable from a perfect dice for many thousands of rolls. Practically speaking, you cannot work out the actual bias of a dice, but you can give yourself statistical evidence that it's less (or more) biased than some given threshold. Even if you automate dice rolls, you're going to have some additional bias from the automated rolling technique which will not properly reflect the dice itself. Dice can be biased in different ways, too. It could be that a given dice is more likely to land on a specific region, as in your theoretical example, in which case, your expectation of being further from the unbiased distribution is correct. But a dice could be biased and land on two opposite clusters most of the time, and, if those clusters are opposites (eg: 20, 19, 18 and 1, 2, 3), you'll wind up with results which look more fair, even if the dice is actually more biased than the single cluster biased dice. If anyone is worried about dice bias, a float test is sufficient. If it's not obviously biased in that float test, for gaming purposes, any bias is simply not going to be relevant, and I'd even personally be comfortable using any float test passing dice for generating key material. Beats the hell out of software RNG. One other practical suggestion for those looking to get unbiased randomness from dice (or coins) is to throw the dice against a vertical surface, rather than rolling them, so it bounces off and then lands on the table, which will eliminate bias from rolling technique.
@@TalsBadKidney I can't say I've tried it, but your dice should have roughly the same buoyancy in beer as in water, maybe with a little lift from bubbles too. You're going to be displacing the same volume of liquid when dropping it in beer, and you might trap some bubbles under the dice, displacing a little extra. The problem is, the float test requires mixing in salt or sugar (salt requiring less for the same buoyancy, but much, much more sugar can be dissolved into the same volume of water, making it better overall), which would be a terrible waste of good beer. 😉
Why would you crap on software RNG? Sure, it's predictable if you know the input parameters, but it behaves exactly like a real randomness. You can have long streaks of the same number just like a real randomness would, but over a million rolls, each number gets rolled roughly the same amount of times. Of course it's not good for security, but for every other application you can safely call it random.
@@hvip4 Because he's in cryptography and talking about generating a key (likely in the context of cryptographic usage). So its literally the specific reason that you said it wasn't good for, that he is saying it's bad for.
Yeah, I would have really liked to just see the distributions. Since there are only 20 outcomes, binning isn't an issue and a plain old histogram would be fine. To be really nerdy and pedantic.. empirical cumulative distributions are usually the thing to use if you want to to compare stochastic things which have lots (or continuous) possible states/outcomes. You can also more easily fit functions to them.
Yeah, I wasn't really satisfied with just an average. Having a lot of 1s and a lot of 20s would still benefit the player more than a spread of 1-20. A 6 is still very likely to fail, and a 15 can still fail. And in games with crits, 20s are usually natural criticals. Median will just be 10 or 11 once you have over a hundred rolls, unless something is severely wrong with the die. A bar chart would've showed the actual distribution. How much each individual number was rolled. I know he had the numbers on the sides, but they weren't even talked about.
One thing to note about statistics is to get to a true distribution of something, you need a sample size that is so large that the thing that happens the least happens at least 30 times in your sample size. if you do that it will bring your t-distribution to the point that is is 95% accurate in comparison to the true z-distribution. so for the perfect case the smallest sample you need to get close to that for a 20 d would be 600 samples as that would be 30 cases of each side. So for your case here the sample 1000 should be counted as close to the true distribution of these cases. This is one of the main things I remember from my stats class when looking at sample sizes and how to tell if something was doing enough sampling to get to a true distribution.
It is facinating to see the testing methods. I personally don't mind if someone has a spindown or a normal D20. If i notice a character has a propensity to cheat. I deal with the player, not find one million different ways to get them to not cheat.
Exactly. If you put a roll down in a cup, it doesn't matter, but use a careful and consistent rolling move and line up the dice in you hand when you "shake" and you can easily get some higher results. It just makes it easier to manipulate.
For finding unbalanced dice, you could drill a tiny hole in each, and then cover up the entrance to the hole with paint. That would change the mass distribution, and also you could forge similarly unbalanced dice, both normal and that other one
When I worked at a game store several years ago, This exact question game up. My Pathfinder group wanted to ban me using the MTG spin-down dice. So I spent a few slow days rolling the spin down 5000 times. I should have done a standard deviation like you, but instead I just used a more crude metric of average rolls, and highest and lowest rolled numbers. I compared this to 9 other sets of 5000 randomly generated dice rolls. Since my dice did not have the highest average or an unexpectedly high number of high rolls compared to the random sample, my group relented, and let me use the die. However, I think they really just wanted to shut me up. I have also confirmed that if you want to cheat, you can finesse the roll for a more favorable outcome on a spin down. In another test, I was able to roll a 20 in 20% (4/20) of rolls, and a 16 or better about 40% of the time after 300 rolls. But this involved holding it just so, and barely letting it tumble out of the hand on a specific surface after several minutes of practice. If you are rolling fairly, your spin down dice should give you just as random of a result, within reason. I say if you have someone cheating with spin down dice in your game, and you ban the dice, they will cheat in other ways, and probably already are.
Spindowns are the easiest possible die to cheat with. The only thing potentially easier is a coin flip. Die are gambling equipment. Any gambling equipment or randomizer that is less secure than THE STANDARD equipment should be banned across the board as essentially the only functional difference is being able to cheat with it easier. This is no different than allowing cards with slightly different design or textures on the back. Spindown die even being made in the first place is massively suspect. A normal d20 is not hard to track life on if you know all sides add to 21.
@@KyleTremblayTitularKtreyit's completely different. You're totally capable of using a spin down legitimately. There's no way to use a set of cards like that without seeing the differences. But even then someone who doesn't know the differences would be able to use the cards just the same as a normal deck. If you don't trust the people you play with not to cheat, just don't play with them. It's pretty simple my guy. Also it's a game. You don't have to take personal games between friends so bloody seriously.
@@KyleTremblayTitularKtreyWhat are the odds of rolling a 20 on a regular d20? I in 20 What are the odds of rolling a 20 on a spin down? 1 in 20. Y’all are making too big a deal out this. The arrangement of the numbers doesn’t change the odds, and the average person, and hell, even most sleight of hand artists, isn’t going to be able to reliably game a spin down. This is a nonissue.
@@Glmorrs1 You're missing the point. Sit down with a spin-down die and a normal die. Don't ~try~ to be fair, ~try~ to cheat with the spindown die, and you will find it's much easier. It's not about the probability, it's about abusibility. Is it a BIG deal? No. Can anybody learn to cheat with them after just a few minutes of practice? Yep.
This video is about exactly the kinds of things that I think about in my head and have no idea how to actually test because I’m not a Maths person. I love how detailed this is and how much you break it down for the non-maths like myself. I’m a new sub just to see what other delightfully detailed information you have!
@@NEEDbacon Fair enough. I found it slightly distracting for this video but each to their own. I had some sound activated colored led lights that I rather enjoyed when listening to music.
@@NEEDbacon I thought it was a candle effect too and just happened to use a really bad/distracting pattern. Didn't realize it was tied to the sound level, that would be cool if it were tied to maybe hue or something instead. Or maybe just a slower on/off so it didn't look like power outages.
Great Video Thanks for sharing. As a dm who later encountered spin downs from folk who played magic I immediately fell in love. Love me some giant MTG dice. With TTRPGs, I'm a lot more selective with who I play with and it's been a nice "can you be chill and hang" measure. Also great counters for things like frosthaven monster hp and such, can see why mtg players use them.
I carry both of these dice, and oddly enough i use a spindown dice as my DM descretion dice because it's easier to control a result to prevent total disaster
^^ the only use case for the spindowns is so the DM can cheat on saves and attack rolls to subtly prevent full party wipes or make his big bads last a bit longer.
@@Muhahahahaz it's easier to manipulate because, if you watch the video, the numbers have a more controlled group. you cant make it land on a number, but you have a better time to get a result you want with it
So here's my take on this: - In any low stakes scenarios, the difference between a spin-down and a Regular D20 are so small as to be nonexistent. - Most spin-downs are made well enough that they *are* just as fair as the average Regular. However: - These dice configurations serve different purposes, and they may be designed with those purposes in mind. A spin-down may have a center weight, and a different surface finish so it's less likely to tip over on accident (f.e. when someone bumps the table) Also they may not be tested for weighting, because gain, they're not primarily designed to be rolled. - Conversely a Regular D20 is specifically designed to be rolled, hence they are more likely to be tested for fairness - *IF* either die configuration happens to favor a side, the Regular D20 will stay "fairer" with increasing bias, hitting a wider range of results, rather than a specific sequence.
Question: are the numbers on these dices always carved in? Because if so, wouldn't spin down dices basically have a production fault since higher numbers have two digits and therefore more material carved out thus unbalancing the dice?
Was thinking the same. Spin down having one area/side with only two digit numbers would move the center of gravity to the singel digit side. Making it inherently unbalanced and more prone to rolling high numbers.
In general, I think the paint is supposed to be weighted to correct for that. That said, I've heard concerns that spindown dice would have less attention given to making them balanced in manufacturing because they're primary intended purpose is for rolling. That said, I think Wizards of The Coast has claimed that their spindowns are balanced for use when rolling, so it's probably fine.
Back in the day, I knew a guy who thought it was cool to melt different colored wax into the number grooves. He said it made the dice easier to read. Back then some dice were pretty plain, but now they come in nearly infinite varieties of colors, sparkly/not sparkly, etc. I questioned whether he'd noticed any difference in the performance of his dice because he'd added weight to them, but he didn't think so. I think we've all had one or two dies that we really liked, because we used them to pull off some incredible feat in a game. I had a d20 that was my favorite, but at the game table I was well known for being either incredibly lucky, or incredibly unlucky. That die was probably biased since I didn't know about float tests back then. In nearly every game we played, I did something great with a 20, or nearly died with a 1. And sometimes both in the same game.
A big thing to note, the idea that spindowns don't roll properly was put forward when most, if not all of them on the market were MTG fat pack spindowns that had an expansion symbol, usually on the 20 position, rather than a number. The specific symbol and how much carve out it requires might affect the roll.
Is it a silly question to ask a 'standard' die has a numbering arrangement that is not spindown, is the relationship between the numbers fixed beyond the requirement that opposite faces add to 21?
It might be a silly question, but I'd also like to know the answer. From my quick search of the internet I learned different manufactures use different patterns. The website "Alea Kybos’ Dice Collection" has a "Configurations" section which shows a bunch of different d20 layouts.
I feel like it doesn't matter at all where the numbers are. But there's a chance for manipulation if you don't have a watchful DM, doing "micro" rolls and/or "flips". but as long as you're yeeting the dice a similar way every time the results should be random.
This entire video missed the point because you were assuming fair rolls. The whole issue is that it is very easy to cheat using a spindown. Test it for yourself, I have. It only takes a few minutes of practice to consistently roll high numbers every time.
@@WalterSMM2I would find out why people cheat before ditching them. For some people it's because they struggle with invisible disabilities. Read a story from someone who DMs public games. Had a player who cheated because they struggled so much with math that adding numbers for attack rolls was hard for them. They were ashamed of this, so instead being vulnerable and risking ridicule by asking for help, they cheated to get pre-calculated results. If the player was able to ask for and receive help, or was in an understanding and caring group who noticed the problem and offered help, the player wouldn't cheat. Even those who cheat for ego reasons can often be talked to and have their underlying issues addressed and the cheating potentially stopped. That said, not everyone has the time, energy or ability to handle cheaters this way, and not all cheaters can be handled this way. I think most cheaters can be helped though.
@@WalterSMM2 That's fine and all, but nobody thinks that a spindown is any less random on a fair roll. The entire issue is that they're easy to cheat with and ignoring that makes the video pointless
I've never heard of this before and don't know how I got here. The algorithmically demanded engagement is hereby complete and I will now watch the rest of the video, thank you.
It's as much physics as probability. The randomization effect of a single die in based on its physical geometry, not the arbitrary label we ascribe to each face. The momentum, shake, throwing position, bounce, etc combine with the uniformity. Every face has roughly a 1 in 20 chance of landing up.
While rolling a die, unless it's weighted, usually evens out the numbers you get. But with that spindown die, you could technically learn the exact way to hold the die to scew the odds in your favor. It will take a while, but if you roll the die the exact same way every time, the way you place the die in your palm gets more important. Seeing how the high numbers are grouped together the odds of rolling a high one gets increased.
I learned how to do this with a regular 6 sided die as a kid, the solution is a backboard that's why casino dice games make you roll them at the backboard first so you cant control them
@@user-ee6lk1pb6w No, because with the spindown dial all the numbers you would want is right next to each other. Making it easier to either roll low or high depending on what you want. On a regular die, low and high numbers are mixed which means you have the same odds getting a low number as a high one no matter how you roll.
I’ve never heard of this before and I have only been playing D&D for 2 months now. But I’ve been going down a rabbit hole of D&D videos trying to learn the game and this video popped up so here I am.
There is a similar test with coins where there is a small unbalance where if you flip a coin it was biased towards landing on the same face. Potentially the dice has a similar bias where it might land towards one face more often if rolled from a specific face. Someone could gain a tiny advantage by rolling from the same face.
I use numerically-balanced d20s and d30s from The Dice Lab. "In the standard d20 numbering, small and large numbers are distributed more-or-less evenly over the die, with the following vertex sums: 39, 47, 49, 51, 52, 52, 53, 53, 54, 56, 58, and 66. Using computer search techniques, we've managed to find a numbering with ideally-balanced vertex sums while retaining the opposite-side numbering convention: 52, 52, 52, 52, 52, 52, 53, 53, 53, 53, 53, and 53."
No idea how I got here and while I'm a board gamer I don't usually play games with d20s, but, your video looks fun and I'll indulge in your invitation to engage. I speculate that they'll be equally random from a blind roll but the spin-down will be easier to chuck in a way that you'd have a better chance of getting your favourable numbers, because of their groupings.
I imagine that so long as they are both rolled fairly, there is little difference. If someone were to purposefully roll unfairly, however, the spindown die might be easier to manipulate into consistently higher rolls.
There is a way to accurately measure this. The perfect theoretical dice is using binomial distribution and we can test it our dice does as well. We should use the Chi2 compliance test to determine whether the dice is actually using the binomial distribution.
I never heard of this before, i don't know how i got here, but after the intro i gotta say, i am truly intrested on listening to you talkjng abou it, go ahead dear stranger!
For your efforts, a like, sub, and ding. I remember having this argument 15 years ago when mtg started giving out spindowns in precon packs. Kind of amazing it's been going this long.
I didn't know any of this before and I don't really know how I got here. You got me soo good with that one I just had to actually leave the comment as you asked 🤣
I think a bigger flaw in this experiment than the small sample and spindown only being slightly unbalances, is that it's starting from a false assumption. This video is actually the first time I've even heard the idea clustering of numbers in spindown could give unbalanced results in a normal roll. The main argument I've always seen is that clustering of numbers on a spindown makes it easier to use a rolling technique that could look fair but increases your likelihood of rolling high.
This is so cool! If you've got a video on float tests, it would be helpful to have a link in the video description. :) (If you don't have a video on float tests, I'd totally watch one if you made it!)
As a Warhammer player, I've never used D20's as anything other then trackers so I've always wanted the ones that have the numbers adjacent in numerical order. My guess before watching video is that if there is a difference in the randomness it's so small that it's negligible
Factors: Cheating. Mathematical Randomness Balance Cheating: you can cheat on regular dice too, even if its harder. More importantly, if you try to cheat on spindowns, its painfully obvious the dice only stayed on one side. MOST IMPORTANTLY consider the priority and motives of people trying to cheat in a casual game for fun. In summary, cheating isnt a good argument against spindowns in practical situations Mathematical randomess: So long as the dice are adequately rolled, both dice will produce a random number from 1-20 without bias. Just roll correctly like you would any other oppositional d20.Summary, spindowns are mathematically random. Balance: you could argue that a spindown is more likely to bias higher or lower rolls based on the ways it is off balance. But the way it is off balance could result in higher rolls, lower rolls, or more medium rolls. or more higher and more lower rolls and less medium. exct. off balance oppositional dice can also do this, if maybe to a lesser degree. Oppositional dice are however not less likely to be imbalanced. Spindowns are generally of high quality, as they generally come from wizards of the coast. i encourage you to try balance testing them. In summary, balance is always an issue with dice, but is less common in spin downs. Verdict: spin downs are perfectly fine for casual use, if an event is competetive, you better be checking every dice and the way theyre being rolled, not just the spindowns.
Hypothesis before seeing the rest of the video: Theoretically, a spindown should have the same odds/randomness as a standard since they have the same amount of sides and the same shape, so each side should have the same odds. But I feel like with enough practice, it could be really easy to manipulate rolls with a spindown to consistently roll high numbers, whereas the mixed layout of a standard die makes it much more difficult to do the same. The next paragraph will be me after I've seen the video. Hello future me, by the way! You look extra cute today. Aww, thanks past, pre-video me! You looked cute too! Anyways, the data was super interesting to see the results of, and I'm honestly a little sad that the spreadsheets weren't linked in the description. I would've loved to see if the "unbalanced" (in quotes because of the well-done manufacturing) spindown die had clusters of similar roll results or if the results would have been as evenly spread out as the balanced standard die. Perhaps my hypothesis would be correct? There's just not enough data to tell, but I did enjoy the video and will be sharing your efforts around to more people. Also, this is my plea for a link to a public form of the spreadsheets for the three sets of rolls 🙏
1:22 I think they are both equally random. Maybe a malicious player could try some tricky roles to get an advantage, but it could be easily solvable with a dice tower.
I love the research you did here. Though one thing that comes to my mind is that with an unbalanced spin down the data might differ based on which side is favored in the unbalancing. I would expect there to be a bigger deviation if the imbalance favored 1,2,3,4,5 or 16,17,18,19,20 as opposed to 8,9,10,11,12.
This was a really cool video, and I'm interested in your automated die-roller project if you ever do build it. Thanks for doing the math for fair/unfair dice, and then spending 4 hours rolling and recording d20s for our edutainment! I did have issues with your audio, you started out fine, then would fade out dramatically then come back to an acceptable level.
Any recommendations for a quality set? I'm new and this, aside from being surprisingly interesting, is another thing to consider in an already mind bending universe. 😅
this is incredibly interesting! my mtg pod only rolls spindowns for heads/tails sorts of rolls because they have equal quantities of odd and even sides. i think that we all were just under the assumption that they are entirely unfair, but its exciting to see the mathematical evidence for that claim!
As was mentioned here in comments already, spindice seems less prone to cheating throws. It's hard to tell how much, but I think it's quite possible to roll dice to get gyroscopic effect to try to keep some part up, or master throw to be more deterministic.
Others have kind of pointed it out, but spindown dice are much easier to cheat with, most people aren't going to enforce good dice rolling practices so you can just side spin them for a higher chance of high rolls.
My initial thoughts: I heard once that whether or not a die is rolled 'fairly' has more to do with how long you actually roll it around in your hand, whether or not you use a dice tower, etc. than the actual rolling across a surface. My instinct is to say that applies here, and that so long as the die is rolled/randomized enough, like thoroughly shuffling a pack of cards, it shouldn't make a difference whether it's standard or spindown.
My guess before I continue with the video is that they'll be equally random, but there might be a false conclusion if one set of data "looks less random" than the other.
An interesting experiment, and kinda highlights a simple point that goes unspoken in this debate - The die has to be rather quite unbalanced before it makes a noticeable difference at all, and that difference won't show up as statistically significant during the span of normal use assuming the die is close to balanced. Combine that with the fact that these dice are inherently made to be at least mostly balanced (it would be silly and wasteful to set up the automated process of production to specifically produce unbalanced dice, so even if quality control is lesser for the spin-down dice than the standard dice, they're both targeting a balanced die as their desired product), and for ordinary usage, the difference between the two becomes negligible. That said, the basic hypothesis is sound in theory. Due to the spread on a standard D20, it should be relatively fair even if the die is slightly unbalanced, while a spin-down D20 has no such considerations for its rolls, and is likely to skew farther in one direction if it's slightly unbalanced. Fun stuff, thank you for putting your time into this!
