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MathGroup Archive 2005

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Re: The two dices

  • To: mathgroup at smc.vnet.net
  • Subject: [mg54492] Re: [mg54486] The two dices
  • From: "Barthelet, Luc" <lucb at ea.com>
  • Date: Tue, 22 Feb 2005 04:22:51 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

When you wrote dice[]+dice[] it became 2*dice[]. That's why you do not
have odd numbers.
By adding a parameter you prevented that simplification and you got the
proper result.

Luc
http://www.mathematica-users.org

-----Original Message-----
From: Antoine [mailto:bugaboo12703 at yahoo.fr] 
To: mathgroup at smc.vnet.net
Subject: [mg54492] [mg54486] The two dices

Hello,

I wanted to simulate the throws of two dices and something happened I
can't
explain:
(Mathematica 5.0 , the same occurs on Mathematica 5.1 )


The following code is OK:


n=300;
theThrows = Table[Random[Integer, {1, 6}] + Random[Integer, {1, 6}],
{n}];
theStats = Table[Count[theThrows, i], {i, 2, 12}]


the occurences, as n becomes greater and greater, looks like the
Gaussian
curve
(sorry for my English)


Suppose you want your dice function, and that it is defined by


dice[]:=Random[Integer, {1, 6}]  ( nothing wrong about it, I suppose )


Now the behavior of the following code changes depending on the value of
n.
If n < 250 everything is fine ...
hen n >= 250, then there is no occurence of odd values.
( the two dices never give 3, 5, ....)


n=250;
theThrows = Table[dice[] + dice[], {n}];
theStats = Table[Count[theThrows, i], {i, 2, 12}]


Does a rationnal explanation exists ?  Is it a bug ?


The two definitions ( see below ) of the dice function "makes" the code
running properly.
But, of course, I prefer the former definition.


dice:=Random[Integer, {1, 6}]  ( not so nice, specially if you want to
have
several dice functions)
dice[_]:=Random[Integer, {1, 6}]   ( you must give a parameter to the
function, quite horrible )


Thank you for your help.
Antoine



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