# Definition of randomness **URL:** \ **Category:** Factual Questions\ **Created:** [February 11, 2003, 5:41pm UTC](https://boards.straightdope.com/t/definition-of-randomness/154388 "2003-02-11T17:41:51Z")\ **Posts on this page:** 12\ **Page:** 2
**Author:** ![murphyboy99](https://avatars.discourse-cdn.com/v4/letter/m/7ba0ec/32.png) [@murphyboy99](https://boards.straightdope.com/u/murphyboy99)\ **Post date:** [February 12, 2003, 1:12pm UTC](https://boards.straightdope.com/t/definition-of-randomness/154388/21 "2003-02-12T13:12:56Z")
If you don’t know the way the series was generated any guess will be inductive. You might think that 1, 1/2,1/3,1/4,1/5… Is the series 1/n but that’s just an inductive guess, and there’s nothing wrong with that, physical laws are inductive guesses too. Sure every time I’ve dropped something it’s fallen down (toward the center of the earth), that doesn’t mean it will next time, but that didn’t stop Newton from formulating the universal theory of gravitation. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [February 12, 2003, 1:40pm UTC](https://boards.straightdope.com/t/definition-of-randomness/154388/22 "2003-02-12T13:40:50Z")
> [@](#): > > \*Originally posted by Urban Ranger \* > **To me, this view is too simplistic. Claude Shannon’s Information Theory is interesting but not complete.** You mean, like, explains everything? O boy, can’t wait. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [February 12, 2003, 3:05pm UTC](https://boards.straightdope.com/t/definition-of-randomness/154388/23 "2003-02-12T15:05:35Z")
> [@](#): > > _Originally posted by Urban Ranger_ > They are not random in the sense that you can generate the next digit through an algorithm, but they are random in the sense that you cannot predict what the next digit is by looking at what all the digits you have now. But the algorithm _itself_ constitutes a formal means of predicting what the next digit will be ! It’s just silly to limit the meaning of prediction to those things that can be deduced by looking at something without a formal plan of analysis. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [February 12, 2003, 4:09pm UTC](https://boards.straightdope.com/t/definition-of-randomness/154388/24 "2003-02-12T16:09:04Z")
(Regarding the digits of Pi not being random in Algorithmic Information Theory.) > [@](#): > > \*Originally posted by Urban Ranger \* > They are not random in the sense that you can generate the next digit through an algorithm, but they are random in the sense that you cannot predict what the next digit is by looking at what all the digits you have now. Umm, if the digits are Pi, then they are not random, if the digits are _not_ Pi they may or may not be random. Go search about “Kolmorgorov” and such. Read up on it. You are missing the whole concept. By the very existence of an algorithm to generate its digits _de facto_ means it’s not random in this context. ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [February 12, 2003, 5:07pm UTC](https://boards.straightdope.com/t/definition-of-randomness/154388/25 "2003-02-12T17:07:37Z")
When a computer scientist says that a sequence of digits is random, (s)he means that it’s incompressible–there’s no program/input pair shorter than the sequence of digits that can produce that sequence of digits. [symbol]p[/symbol] is not random, because it’s infinitely long, but can be produced by a finite algorithm. 1 is random, because even the statement “output 1” is longer. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [February 12, 2003, 5:28pm UTC](https://boards.straightdope.com/t/definition-of-randomness/154388/26 "2003-02-12T17:28:40Z")
> [@](#): > > \*Originally posted by ultrafilter \* > \*\*1 is random, because even the statement “output 1” is longer. \*\* So, would [symbol]p[/symbol] be random, then, because “output [symbol]p[/symbol]” is longer? 🙂 ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [February 12, 2003, 5:32pm UTC](https://boards.straightdope.com/t/definition-of-randomness/154388/27 "2003-02-12T17:32:38Z")
> [@](#): > > \*Originally posted by RM Mentock \* > \*\*So, would [symbol]p[/symbol] be random, then, because “output [symbol]p[/symbol]” is longer? 🙂 \*\* 😛 Of course, I’m talking about representations in base 10 here. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [February 12, 2003, 5:52pm UTC](https://boards.straightdope.com/t/definition-of-randomness/154388/28 "2003-02-12T17:52:24Z")
I thought you were talking about representing numbers in a compressed form? That’s certainly a different representation, right? ---
**Author:** ![Trigonal\_Planar](https://avatars.discourse-cdn.com/v4/letter/t/0ea827/32.png) [@Trigonal\_Planar](https://boards.straightdope.com/u/Trigonal_Planar)\ **Post date:** [February 12, 2003, 7:31pm UTC](https://boards.straightdope.com/t/definition-of-randomness/154388/29 "2003-02-12T19:31:02Z")
And I thought you meant representing numbers by an algorithm. Pi can be repressented in compressed form by an algorithm; a “truly random” set of numbers could not be. ---
**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:** [February 12, 2003, 11:10pm UTC](https://boards.straightdope.com/t/definition-of-randomness/154388/30 "2003-02-12T23:10:08Z")
> [@](#): > > 2, It depends how quickly the average number guessed converges to 0.5 (as we increase the number of guesses). I like this one slightly more because we can compare it to other converging series, but the series will not always converge at the same rate. Since nobody’s covered this yet, let me point out that this would not be a very useful test. I can write a program that always outputs 0.5, which would converge very quickly indeed, but which would not satisfy any reasonable definition of randomness. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [February 13, 2003, 1:00am UTC](https://boards.straightdope.com/t/definition-of-randomness/154388/31 "2003-02-13T01:00:52Z")
A sine function with an amplitude of 1 would be a little more elaborate way to mess with possibility 2. ---
**Author:** ![man779977](https://avatars.discourse-cdn.com/v4/letter/m/59ef9b/32.png) [@man779977](https://boards.straightdope.com/u/man779977)\ **Post date:** [February 13, 2003, 3:06am UTC](https://boards.straightdope.com/t/definition-of-randomness/154388/32 "2003-02-13T03:06:27Z")
Maybe random numbers only exist in the minds of those that cant think (insane), because people think generally in patterns until there mind becomes damaged [Previous page](https://boards.straightdope.com/t/definition-of-randomness/154388.md?page=1)