# Using dice to pick 10 numbers randomly **URL:** \ **Category:** Factual Questions\ **Created:** [June 9, 2014, 8:22am UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392 "2014-06-09T08:22:48Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [June 9, 2014, 4:00pm UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/41 "2014-06-09T16:00:38Z")
> [@sbunny8](#): > > But then again, I only have a master’s degree in mathematics, not mathemagics. We all have regrets in life. ---
**Author:** ![The\_Hamster\_King](https://avatars.discourse-cdn.com/v4/letter/t/8edcca/32.png) [@The\_Hamster\_King](https://boards.straightdope.com/u/The_Hamster_King)\ **Post date:** [June 9, 2014, 4:08pm UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/42 "2014-06-09T16:08:52Z")
> [@jtur88](#): > > Put a small hole in the center of the table, so a few dice fall through, which can be disregarded. That will bring it a lot closer to random by flattening out the curve. Ideally you should have a table that gently slopes in the shape of an inverted bell curve down to the hole in the middle. The closer the die lands to the center of the distribution, the more likely it is to be bounced in the hole and discarded. :rolleyes: ---
**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\ **Post date:** [June 9, 2014, 4:43pm UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/43 "2014-06-09T16:43:01Z")
[If you’ve got $64.70 burning a hole in your pocket…](http://www.amazon.com/Million-Random-Digits-Normal-Deviates/dp/0833030477/ref=sr_1_1?s=books&ie=UTF8&qid=1402332124&sr=1-1&keywords=random+digits) ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [June 9, 2014, 4:55pm UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/44 "2014-06-09T16:55:48Z")
> [@Tastes\_of\_Chocolate](#): > > One roll - 5 six-sided dice, (or roll your 2 dice 2.5 times!) add them together, divide by 3 and round up to the nearest whole number. > 1-3 = 1 > 4-6 = 2 > 7-9 = 3 > … > Assuming balanced dice, you will get an even distribution of answers. As **The Hamster King** showed, that’s not even close to uniform. Maybe you’re misremembering, and instead of dividing by 3, you should take the result modulo 10 and use 0 for 10. So if your sum was 6, 16, or 26, for example, that would count as a six. Testing this, the probability of each value 1 to 10 only varies by about +/- 8 percent from uniform. ---
**Author:** ![DataX](https://avatars.discourse-cdn.com/v4/letter/d/e99b99/32.png) [@DataX](https://boards.straightdope.com/u/DataX)\ **Post date:** [June 9, 2014, 6:57pm UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/45 "2014-06-09T18:57:59Z")
> [@gazpacho](#): > > Casino dice do not have pits taken out of them for spots. The spots are painted on or are stickers. Nitpick - they do have pits taken out of them AND they are painted with a paint with the same specific gravity as the dice themselves. [look at lower left hand die - as you probably know - both sides of a proper die add to 7 - so you can see the paint on the side opposite the “one” have depth to them](http://thumb7.shutterstock.com/display_pic_with_logo/577552/577552,1294025662,1/stock-photo-close-up-of-colorful-las-vegas-nevada-casino-gambling-dice-on-a-white-background-68153569.jpg) Otherwise - the paint itself would bias the die - granted to a much, much, much smaller amount than regular pitted pips would. As far as using ten sided dice - they are almost certainly not of sufficient quality to be random. [This guy](http://dicephysics.info/0107.htm)made a machine that rolled dice tens of thousands of times and shows the results for both cheap dice and casino dice. You don’t have to be a statistician to see how poor the cheap quality dice performed. To me the easiest method (and the one used by [at least some] in the crypto community) is to make a 6 x 6 grid and you’d use two visually different die (say blue and red). You’d roll both at the same time - say using the red die as row and the blue die as column. The columns could be arranged like: 1:3:5 1:3:5 1:3: (and so on) 2:4 2:4 2:4 Or 1:7 2:8 3:9 4:10 5:1 6:and so on So that the first five columns (30 spaces) were filled with integers 1 thru 10 - three times each- and the sixth column would be roll again. I think others alluded to this method above. You roll both dice at once - and only need to reroll 1/6th of the time. This is vaguely similar to the method used by rand in their literary classic mentioned above “A Million Random Digits and 100,000 Normal Deviates”\*. Their method of getting the number involved obtaining a random five bit binary result - which gave them a decimal number between 1 and 32. They discarded numbers 21 - 32 and used the second digit of numbers 1-20 as the digit. Depending on what you are using it for - I think the Excel method is much easier. While they aren’t “truly random” - I have never noticed any issues (I have in early versions of excel - as well as the default random number generator in PGP). I certainly wouldn’t use it for picking seed numbers for say something to do with cryptography. [Random.org](http://Random.org) is cool - I highly recommend reading the reviews of that book on Amazon - certainly entertaining. ---
**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\ **Post date:** [June 9, 2014, 7:09pm UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/46 "2014-06-09T19:09:25Z")
> [@jtur88](#): > > Roll 1,000 dice and add them up. Use only the last digit of the sum. Not perfect, but close enough for practical random number generation. Disappointingly slow method, though. Zero wil be slightly more prevalent, at the peak of a bell curve that favors 3,500. Put a small hole in the center of the table, so a few dice fall through, which can be disregarded. That will bring it a lot closer to random by flattening out the curve. I find it’s easier to fly to Monte Carlo, and pay someone to run a “Them” Simulation. Or get a [Zocchihedron](https://en.wikipedia.org/wiki/Zocchihedron), divide by 10, and round. That would also probably take care of the unevenness, too. Or Excel, use the =RANDBETWEEN(1,10) 1000x (or even better, 10,000x) in Column A. Then somewhere else use =COUNTIF(A:A, “1”); =COUNTIF(A:A, “2”); and so on (or a reference to the integer in place of the quotes). ---
**Author:** ![jtur88](https://avatars.discourse-cdn.com/v4/letter/j/e9c0ed/32.png) [@jtur88](https://boards.straightdope.com/u/jtur88)\ **Post date:** [June 9, 2014, 8:46pm UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/47 "2014-06-09T20:46:09Z")
> [@jtur88](#): > > Roll 1,000 dice and add them up. Use only the last digit of the sum. Not perfect, but close enough for practical random number generation. Disappointingly slow method, though. Zero wil be slightly more prevalent, at the peak of a bell curve that favors 3,500. Put a small hole in the center of the table, so a few dice fall through, which can be disregarded. That will bring it a lot closer to random by flattening out the curve. I’ve refined this. Make the hole large enough that the number that falls through is about 75, plus or minus a dozen or two. Then just count the dice that fell through (usually between 50-something and 90-something), and use the last digit of that number. No need to even count the spots on the dice. ---
**Author:** ![Jragon](https://avatars.discourse-cdn.com/v4/letter/j/e19b73/32.png) [@Jragon](https://boards.straightdope.com/u/Jragon)\ **Post date:** [June 9, 2014, 8:47pm UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/48 "2014-06-09T20:47:44Z")
Murder a bunch of people, select the number you get before the police catch you modulo 10 + 1. ---
**Author:** ![Buck\_Godot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/buck_godot/32/6573_2.png) [@Buck\_Godot](https://boards.straightdope.com/u/Buck_Godot)\ **Post date:** [June 9, 2014, 8:54pm UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/49 "2014-06-09T20:54:14Z")
> [@Arrogance\_Ex\_Machina](#): > > The full D&D dice set was one of each die from d4 to d20, including a d10. And of course there’s a lot of systems using d10s nowadays since it is an easy way to roll d100, so yeah they should be fairly common. Sorry have to disagree. The d10 appeared some time after the AD&D books came out, I remember being very surprised when I first saw them. Not being a platonic solid it wasn’t obvious how to make one. Also to get a 1-10 result, you could just use the 20 sided die. Especially true since it just went from 0-9 and you had to color half of the faces yourself with a permanent marker that would mean “add 10” to the result. Sigh, kids these days. ---
**Author:** ![Superhal](https://avatars.discourse-cdn.com/v4/letter/s/b4bc9f/32.png) [@Superhal](https://boards.straightdope.com/u/Superhal)\ **Post date:** [June 9, 2014, 9:07pm UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/50 "2014-06-09T21:07:22Z")
Yeah I think any other dice except 6 sided dice meant for gambling has not gone through the same rigor in balancing, and thus wouldn’t be useful. I just went and looked at 4 different stores selling souvenir dice, and I’d guess about 2/3 hasn’t been balanced looking at the amount of inscription and text they contain. ---
**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\ **Post date:** [June 9, 2014, 9:42pm UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/51 "2014-06-09T21:42:37Z")
> [@thelurkinghorror](#): > > I find it hard that a d10 cannot be found. Older D&D didn’t use it much in favor of d20, but other systems do. I had a basic D&D (e.g. not AD&D) set as a kid and it had at least d4, d6, d8, d12, and d20, although don’t remember d10. > [@Arrogance\_Ex\_Machina](#): > > The full D&D dice set was one of each die from d4 to d20, including a d10. And of course there’s a lot of systems using d10s nowadays since it is an easy way to roll d100, so yeah they should be fairly common. > [@Buck\_Godot](#): > > Sorry have to disagree. The d10 appeared some time after the AD&D books came out, I remember being very surprised when I first saw them. The version of the D&D Basic Set I had, which looked like [this](https://www.acaeum.com/ddindexes/setpages/setscans/basic9rule.html), came with a set of 6 dice, including a d10; but earlier versions only included 5 dice (or none at all). [This link](https://www.acaeum.com/ddindexes/setpages/basic.html) lists the contents of the various editions of the Basic Set; and [here’s a chart](http://en.wikipedia.org/wiki/Editions_of_Dungeons_%26_Dragons) showing the publishing history of the various versions of D&D vis a vis AD&D. ---
**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\ **Post date:** [June 9, 2014, 10:13pm UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/52 "2014-06-09T22:13:10Z")
Interesting link. As I recall, the one I had had the dragon in color on the cover of the box and in blue tones on the manual cover. I don’t remember a d10. ---
**Author:** ![OldGuy](https://avatars.discourse-cdn.com/v4/letter/o/3bc359/32.png) [@OldGuy](https://boards.straightdope.com/u/OldGuy)\ **Post date:** [June 9, 2014, 11:45pm UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/53 "2014-06-09T23:45:52Z")
> [@Buck\_Godot](#): > > Not being a platonic solid it wasn’t obvious how to make one. It’s quite easy to make any dn dice that is fair (in theory it might take some work to balance same). To do this use an equilateral equiangular n-gon and make an n-sided pyramid from it in both directions. Label the 2n sides 1 to n twice. Or if you prefer for n even you can start with an n/2 sided equilateral equiangular polygon. If n is too small and the die doesn’t roll well, use 2n, etc. sides to start. ---
**Author:** ![The\_Hamster\_King](https://avatars.discourse-cdn.com/v4/letter/t/8edcca/32.png) [@The\_Hamster\_King](https://boards.straightdope.com/u/The_Hamster_King)\ **Post date:** [June 10, 2014, 12:03am UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/54 "2014-06-10T00:03:48Z")
Here’s a photo of my first set of poly dice, purchased in summer 1976 along with the white box. No d10. > ---
**Author:** ![Kobal2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kobal2/32/20_2.png) [@Kobal2](https://boards.straightdope.com/u/Kobal2)\ **Post date:** [June 10, 2014, 12:18am UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/55 "2014-06-10T00:18:44Z")
You don’t actually need a d10 to roll a d10, BTW. Pick up a book, any book, though one with 200+ pages would be best. Open to a random page. Use the second-to-last digit of the page number as an odds/even binary toggle, telling you to use the page number of either the left or right page. The last digit of that page’s number is your d10 (0 being 10 obviously). ---
**Author:** ![Darth\_Panda](https://avatars.discourse-cdn.com/v4/letter/d/ee7513/32.png) [@Darth\_Panda](https://boards.straightdope.com/u/Darth_Panda)\ **Post date:** [June 10, 2014, 12:50am UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/56 "2014-06-10T00:50:47Z")
> [@Buck\_Godot](#): > > Sorry have to disagree. The d10 appeared some time after the AD&D books came out, I remember being very surprised when I first saw them. Not being a platonic solid it wasn’t obvious how to make one. Also to get a 1-10 result, you could just use the 20 sided die. Especially true since it just went from 0-9 and you had to color half of the faces yourself with a permanent marker that would mean “add 10” to the result. > > Sigh, kids these days. **Arrogance Ex Machina** is probably referring to the Basic Box Set which came out in 1981, which did include include a 10 sider. AD&D 1ed came out from 1977 to 1979 in three separate books, not in a box set. From page B4 of the Basic Boxset (the 1981 version, which was revised but not retitled): > [@](#): > > Dice included in this set are a 4-sided die, a 6-sided die, an 8-sided die, a 10-ten sided die, a 12-sided die, and a 20-sided die. For easy reading, all of the dice are marked with numbers instead of pips (dots). > \ > The 0 on the d10 is read as “10.” The 1ed AD&D Dungeon Master’s guide was printed in 1979 and included the use of the d20 you described on pages 9 and 10. ---
**Author:** ![Darth\_Panda](https://avatars.discourse-cdn.com/v4/letter/d/ee7513/32.png) [@Darth\_Panda](https://boards.straightdope.com/u/Darth_Panda)\ **Post date:** [June 10, 2014, 12:59am UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/57 "2014-06-10T00:59:50Z")
Missed edit window: Page 10 of the 1ed DM’s guide from 1979 goes on to say: > [@](#): > > Non-platonic solid-shaped dice are available in some places. The most common of these is the ten-sided die numbered from 0 to 9. So, there you have it. The method you described was used, but 10 sided dice were in existence during AD&D’s first run, and were common enough to be included in the Basic Box Set by 1981. They say memory is the first thing to go… ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 10, 2014, 2:11am UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/58 "2014-06-10T02:11:51Z")
You really can’t say that “d10s are too low in quality to give good random numbers”. Like any other product, they vary in quality. Some are garbage, and some are very high quality. There’s no inherent reason that the quality of a die should depend on its number of sides. ---
**Author:** ![Superhal](https://avatars.discourse-cdn.com/v4/letter/s/b4bc9f/32.png) [@Superhal](https://boards.straightdope.com/u/Superhal)\ **Post date:** [June 10, 2014, 8:33am UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/59 "2014-06-10T08:33:29Z")
> [@Chronos](#): > > You really can’t say that “d10s are too low in quality to give good random numbers”. Like any other product, they vary in quality. Some are garbage, and some are very high quality. There’s no inherent reason that the quality of a die should depend on its number of sides. I doubt any die matches the quality of those used in casinos, particularly those that come with board games. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [June 10, 2014, 11:15am UTC](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392/60 "2014-06-10T11:15:03Z")
> [@2gigch1](#): > > If you only have six sided dice, here is the simplest method of non-curved results I can figure: > > Roll 2 six sided dice: > Take the result of the first die from 1-5; 6 means re-roll the dice. > If the second die shows 4-6, add 5 to the result of the first die, otherwise just take the result of the first die. > > This method gives a 1 in 6 chance of re-roll, otherwise it keeps results curve free. In other words, use the solution provided in Post #2. [Previous page](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392.md?page=2) [Next page](https://boards.straightdope.com/t/using-dice-to-pick-10-numbers-randomly/690392.md?page=4)