An experiment in which two or more interventions, possibly including a control intervention or no intervention, are compared by being randomly allocated to participants. In most trials one intervention is assigned to each individual but sometimes assignment is to defined groups of individuals (for example, in a household) or interventions are assigned within individuals (for example, in different orders or to different parts of the body),
The arbitrary process through which eligible study participants are assigned to either a control group or the group of people who will receive the intervention (Chinman et al. 2004).
Non-randomised controlled trial:
A clinical trial with a control group in which patients are not put in the study or control group by chance (randomisation). Instead, they are sorted using other methods.