4. Marbles

4.1 Introduction

These methods use a set of objects, the randomness is given by the odd of picking one object of a given kind.

4.2 Sixteen marbles (copied from Clarity)

Materials
16 marbles in four colours:
  • Five of the first colour, which represent the line
  • Seven of the second colour, which represent the line
  • Three of the third colour, which represents the line
  • One of the fourth colour, which represents the line
Usage            
Put all the marbles in a bag or bowl, and draw one out at random to select the line. After each line, replace the marble in the receptacle.
Comment
This is the easiest way of emulating yarrow stalks' odds.
   Prob( ) = 1/16 = 0.0625
   Prob( ) = 7/16 = 0.4375
   Prob( ) = 5/16 = 0.3125
   Prob( ) = 3/16 = 0.1875

   Prob( or ) = 8/16 = 0.5
   Prob( or ) = 8/16 = 0.5
 
   Prob( -> ) = 1/8 = 0.125
   Prob( -> ) = 3/8 = 0.375

The outcome are the same up to far less than 1/100 (look at the comparison table)

  Marbles Yarrows Coins
0.0625 0.0663 0.125
0.3125 0.3163 0.375
0.4375 0.4337 0.375 
0.1875 0.1837 0.125
Variation

The image on the right shows the beads string that I use. It's small, portable and very useful as anti-stress! Pick a bead at random,

  • if it's the single black, you got
  • if it's one of three brown, you got
  • if it's one of the seven black you got
  • if it's one of the five brown you got

4.3 Ten marbles (thanks to Dee)

Materials
10 marbles in four colours:
  • Four of the first colour, which represent the line
  • Four of the second colour, which represent the line
  • One of the third colour, which represents the line
  • One of the fourth colour, which represents the line
Usage         
Put all the marbles in a bag or bowl, and draw one out at random to select the line. After each line, replace the marble in the receptacle.
Comment

   Prob( ) = 1/10 = 0.1
   Prob( ) = 4/10 = 0.4
   Prob( ) = 4/10 = 0.4
   Prob( ) = 1/10 = 0.1

   Prob( or ) = 5/10 = 0.2
   Prob( or ) = 5/10 = 0.5
 
   Prob( -> ) = 1/5 = 0.2
   Prob( -> ) = 1/5 = 0.2

This method is symmetric as the three coins one, but give less moving line (chance 10% instead of 12.5%).