Zelen’s design
a type of randomized clinical trial in which patients are assigned to experimental conditions before they have consented to participate in the research. There are two versions of the design, both of which remain ethically controversial: In the single-consent strategy, patients assigned to the experimental treatment are told there is an alternative (the control) available and offered the option to switch; those in the control group are not informed of their study participation. In the double-consent strategy, both the experimental and control groups are offered the option to switch from the treatment to which they initially were assigned. [Marvin Zelen (1927– ), U.S. biostatistician]