• Identifying each animal with a unique identification number, then drawing numbers "out of a hat" and randomly assigning them in a logical fashion to different groups. For example, the first drawn number is assigned to group 1, the second to group 2, the third to group 1, the fourth to group 2, and so forth. Dice or cards may also be used to randomly assign animals to experimental groups.
• Using random number tables or computer-generated numbers/sampling to achieve randomization.