Randomization is the process of making something random. It is remarkably difficult to make anything truly random, as most physical processes and human thoughts and actions, whilst subject to randomness, are much less random than is commonly supposed.

Randomization is used extensively in the field of gambling. Imperfect randomization may allow a skilled gambler to have an advantage, so much research has been devoted to effective randomization. A classic example of randomization is shuffling playing cards.

Randomization is also required in the generation of random numbers for scientific research and cryptography. Hardware random number generators are used for these purposes.

Computers are particularly hard to use for randomization, as their basic design is to be highly predictable devices. There is a temptation to use pseudo-random numbers for randomization: in many applications, particularly those involving cryptography or gambling, this is a major mistake, as pseudo-random numbers are in reality not random at all. John von Neumann observed in 1951 that "Anyone who considers arithmetical methods of producing random digits is, of course, in a state of sin".

Methods used for randomization:

  • casting yarrow stalks (for the I Ching)
  • throwing dice
  • drawing straws
  • shuffling cards
  • roulette wheels
  • drawing pieces of paper or balls from a bag
  • "lottery machines"
  • observing atomic decay using a radiation counter
  • etc.