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Wonderful. You can get so much Maths out of probability. The fifth most popular page on my personal Web site is

http://sohcahtoa.org.uk/pages/rolling-two-dice-experiment.ht...

Off-hand, I would say you can't use chi-square unless you rolled at least 360 pairs of dice. Chi-square assumes a normal distribution and the rule-of-thumb you need at least ten hits and ten misses before the sample distribution approaches normal. Source: just helped my daughter pass her AP Stat mid-term.
We are getting there (250 rolls now), I'll put the extra throws up. Your finding may come as a surprise to many geneticists however...
It's common practice that the 'expected' values of a chi-squared test should be 5 or higher, with adjacent groups to be merged until this is the case (at UK A-level this is strictly required).

This is a slightly conservative correction and Wikipedia agrees that no correction is required in this case: https://en.wikipedia.org/wiki/Pearson%27s_chi-squared_test#P...

This is as likely a magical object as a gaming die.

Glass would have been expensive for a mere gambling device, whereas bone dice were cheap.

It's a Platonic solid found in Egypt, the epicenter of Neoplatonism.

And the symbols on the sides are astrological.

Fair enough on the symbols being astrological, but we do know the Romans used gaming dice. One of my favorite exhibits at a museum I visited in Bath was a pair of wooden dice from a Roman camp. There were two very cool things about them: they used the same dot pattern that we use today, and, as the plaque informed us, they were loaded, rolling 6 significantly more often than the other numbers.
Not surprised that they were loaded that way; the 6 side has the most material removed, so it's the lightest. A fair die needs to be counter-balanced.
I believe the dots were painted, not pitted.
In retrospect, those might just be Greek letters written a little fancy rather than astrological symbols. For instance, the circle with a dot could easily be a theta rather than a sun symbol. Current-day astrological glyphs don't seem to be well-attested before the middle ages.
Magical, in the sense of an Oracle casting a prediction. Which makes it pretty much the same as a D&D dungeon master rolling to determine the outcome of an event, except the players (and maybe the DM) believed it was real.
Could have been rolled as an oracle. Although glass strikes me as not the best material for that. Especially ancient glass that didn't have all of the chemical strengtheners that modern glass does

It might have been just an object of contemplation. Like, you can see how all of the heavenly bodies fit snugly into a perfect geometric figure and just wonder at it.

If there's any rhyme or reason to how the symbols are arrayed on the sides, it could have been a mnemonic or instructional device for casting horoscopes.

And, while it's probably too opaque to have been used for scrying, there's that too.

Dude (or dudette?), what do you practice?

(Can take this to PM if you prefer).

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In Middle Ages and before, games and magic and religion weren't separated.

Even mundane games played in taverns were magically bound to your luck and well-being. More sophisticated (board) games were outright sacred and were seen as a way to communicate with gods.

It's a twenty-sided die; a wet dream of any d&d player.

Hidden bonus: +1 on any roll

With that die I'd crit on every toss.
Pity the British museum doesn't make a nice replica of that I know a few gamers who woudl buy them.
I wonder how biased it is, and what lengths they took to make it unbiased.
Do I hear a authentic reproduction kickstarter?
> Acquired by the current owner's father in Egypt in the 1920s

I think the ethics of trading such goods (at high prices) are bit questionable. It is a piece of local cultural heritage which more than likely was acquired in a more or less exploitative way.

There are similar dice on display at the Met in New York: http://www.metmuseum.org/Collections/search-the-collections/...

Description: "A number of polyhedra made in various materials are known from the Roman world. They may have been used in conjunction with an oracle inscribed on a pillar set up in a public place. The polyhedron was thrown in order to choose a letter at random. One consulted the inscription to find the matching letter and read the oracle's response. There would be twenty oracular messages, each beginning with a letter of the alphabet that corresponded to one side of the dice."

That description makes it sounds like an early version of the magic 8-ball.
If you look closer, even the symbols match up in placement. Indeed, they are identical.
Did Romans play at D&D???
Glass. One of the most expensive things in the Republic and Imperialist Roman era. That dice would be part for sure of a wealthy roman owner.
I recognize the symbol ☉ for gold (or sun) on one of the 20 faces, namely a circle with a dot in the middle (encoded in unicode as 2609 or in html as 9737).

Does anybody know what symbols appear on the other 19 faces of this die?

Also, has anybody run a Chi-Square test for determining the fairness of this die??? I wouldn't pay $17,925 for a loaded die.

Game produced in 1991 sells for $91k+ on eBay, gaming device made in 2nd century AD sells for almost $18k on Christies. Should have tried to sell it on eBay first.
Fake like those crystal skulls ?