randomized

Definition of randomized clinical trial
National Cancer Institute

randomized clinical trial

(RAN-duh-mized KLIH-nih-kul TRY-ul)
A study in which the participants are divided by chance into separate groups that compare different treatments or other interventions. Using chance to divide people into groups means that the groups will be similar and that the effects of the treatments they receive can be compared more fairly. At the time of the trial, it is not known which treatment is best.

Source: NCI Dictionary of Cancer Terms