(randomized) When referring to an experiment or clinical trial, the process by which animal or human subjects are assigned by chance to separate groups that compare different treatments or other interventions. Randomization gives each participant an equal chance of being assigned to any of the groups.

The allocation of individuals to groups by chance, especially in order to control the variables in an experiment.

The process of assigning trial subjects to treatment or control groups using an element of chance to determine the assignments in order to reduce bias. NOTE: Randomization can be executed according to imposed rules to achieve desired distribution. For example, unequal randomization is used to allocate subjects into groups at a differential rate, e.g., three subjects may be assigned to a treatment group for every one assigned to the control group.

(random allocation) A process involving chance used in therapeutic trials or other research endeavor for allocating experimental subjects, human or animal, between treatment and control groups, or among treatment groups. It may also apply to experiments on inanimate objects.