Forum adverts like this one are shown to any user who is not logged in. Join us by filling out a tiny 3 field form and you will get your own, free, dakka user account which gives a good range of benefits to you: No adverts like this in the forums anymore. Times and dates in your local timezone. Full tracking of what you have read so you can skip to your first unread post, easily see what has changed since you last logged in, and easily see what is new at a glance. Email notifications for threads you want to watch closely. Being a part of the oldest wargaming community on the net. If you are already a member then feel free to login now.

I don't know why anyone should ever expect to get the median. You should, after a large number of trials, expect to get the expected value, hence the name. But like I said, whatever he was in fact expecting is completely irrelevant, because what he did was roll a bunch of dice and record the results. He's not reporting what he thought he would get; he's reporting what he did get.

Anyway, I will agree with you that the study was not up to full academic rigor. I don't think it was trying to be -- it was just an experiment to give us some information about the dice we use to play games. What I will not agree with is that we cannot draw simple, qualitative conclusions. A student shaking a dice in his hand is a sufficiently random starting configuration that it should not introduce enough bias to give an end result that should have an almost 0 probability of occurring.

ShumaGorath wrote:

NoobLord wrote:Actually no. IIRC, there was this guy on Warseer who actually tested this out. He rolled a standard GW dice (with pips and curved edges) and then he done the same with a casino dice (pipless & square).
to explain Shuma's question... Standard GW dice have pips - wholes drilled out in them to indicate numbers. Now imagine you roll a dice. You let it go and when you do, it picks up the air and traps it in the pips. Now, don't forget about curved edges - they make the dice spin, jump and do all sorts of gymnastics. Which leads to the air not being able to leave the pips, as there's moving air all around it. Almost like you not being able to drive onto the main road because of traffic. Now, some people already could've worked it out. think you're not cheating? Well, the Dice Gods are. Why? Because they're weighing down each side. And since air does have weight, it weighs the side with the "6" on it the most. And what's on the other end of the 6? 1...which is also the lightest side, and therefore comes up most often.
Another thing I didn't mention, is that stjon said, in a perfect world every side would have a 16.666% chance of rolling. In GW dice, 1 has an AVERAGE 30% chance of rolling. And Casino dice, have an avergage 16% chance. why 16% and not 16.666%? Because Casino dice are fragile, and the sharp bits in the corners often snap off, making slight imperfections. So it's not exactly a pink world.
So, to sum up. Pips are bad. Curves aren't that bad, but pips + curves = very bad. Which also makes Casino dice most fair dice in the world - no pips means no weighing down, and no curves - no rolling of the table .



P.S. Please realise, that the "technical data" I'm putting down is what I can remember from the thread on Warseer.

Doesn't that imply that air is heavier than the plastic used in these dice? An air pocket will not increase the weight of whatever surrounds it unless the air itself is somehow more dense than the surrounding atmosphere (pressurized or cold air). If the study was accounting for drag coefficients and not weight than I can wrap my head around it, though the math would be highly suspect. However the mass of the air within the sixes pips is not logically dense enough to cause the six to orient itself downwards. This still doesn't make a whole lot of sense to me.

you beat me to it!

not to mention that unlike holding a bucket of water, the air around the dice would support the air in the pips. I do not see anyway that the air way's more then the plastic.

if you fill the little pips with lead then you got an argument but thats just dumb.

Does anyone know the effects a dice tower has on probability when rolling of GW/Chessex/Casino dice? I imagine that it would be similar to hitting the lip when rolling Vegas dice: disrupting the "setting down the dice" effect...

I regularly use a dice tower with three levels for the dice to tumble off and a waiting tray for the dice to spill on since my son has horrible dice throwing skills and spends more time chasing the dice than actually rolling them.

shirou wrote:I don't know why anyone should ever expect to get the median. You should, after a large number of trials, expect to get the expected value, hence the name. But like I said, whatever he was in fact expecting is completely irrelevant, because what he did was roll a bunch of dice and record the results. He's not reporting what he thought he would get; he's reporting what he did get.

Anyway, I will agree with you that the study was not up to full academic rigor. I don't think it was trying to be -- it was just an experiment to give us some information about the dice we use to play games. What I will not agree with is that we cannot draw simple, qualitative conclusions. A student shaking a dice in his hand is a sufficiently random starting configuration that it should not introduce enough bias to give an end result that should have an almost 0 probability of occurring.

The study is interesting, but the main problem is that we can't see the whole dataset. Though there appears to be significant variation between Chessex dice and GW dice overall, we don't know the variation within those groups. Do all GW dice roll about 29% ones? No, there a variation there of between 23% and 33%. But we don't know the spread, all that is said is that "We removed any statistical anomalies and came up with 29%." So there's a problem with variance here, both for the rolls of individual dice and between dice of the same set (we only know the outliers, 23% and 33%). Chessex dice and GW dice may appear different, but the variance within those datasets may wipe out the statistical significance of it.

Though if the smallest was 23% that's still well more than you'd expect of 16% if they were totally fair. I can't see a statistical test being applied anywhere, but even not knowing the standard distribution or skew of the data and that large variance, with this number of dice being rolled and such a large difference from the expected result, I'd guess there is clear "significant difference".

There could also be an effect from the way the dice are thrown. I assume that all testers got to have an equal go throwing all dice, and that one person didn't throw all the GW ones and another all the Casino ones. People could have an affect on the way dice are thrown, as an extreme example the results a die throws can be effectively manipulated through controlled dice shots.

The only other problem I see is that the dice in each case have come from the same source, a cube of chessex and a box of GW dice, which implies they were all manufactured together. So imperfections in the dice tested may be common to all those tested, but not common across the whole range. I'm not saying it's probable, but it's certainly not impossible.