Randomization refers to the process of assigning clinical trial participants to therapy or control arms of the trial by chance rather than by choice. This is done to avoid any participant or investigator bias in assigning participants to get one treatment or another. The effects of each therapy are compared at specific points during a trial. If one treatment is found superior, the trial may be stopped so that the most participants receive the more beneficial therapy.
Unequal randomization is used to allocate participants into groups at a differential rate; for example, three paticipants may be assigned to a treatment group for every one participant assigned to the control group.
ClinicalTrials.gov Glossary of Common Site Terms
NIH Clinical Research Trials and You The Basics: What do the terms placebo, randomization, and blinded mean in clinical trials?