The motivation for a typical clinical trial is to provide evidence that a proposed (novel) treatment is superior to the established treatment. A clinical trial fits into the scheme of testing the hypothesis that the average treatment effect is zero or negative against the alternative that it is positive. The purpose of a clinical trial is to choose one of two available courses of action: to proceed towards production and distribution of the proposed (novel) treatment or to abandon the development. A developer may propose a treatment that could for all clinical purposes be regarded as equivalent to an established treatment. When a subject receives only one of the two treatments that are compared in a clinical trial, the corresponding potential outcome is realised and the other potential outcome is not. The rationale for randomisation to treatment regimes carries over from clinical trials with single-treatment administration.