Impact Evaluation of Forest Conservation Programs: Benefit-Cost Analysis, Without the Economics", Environmental and Resource Economics, 1-14. Proc Natl Acad Sci USA, 110 (29). International Initiative for Impact Evaluation, Working Paper 3, New Delhi, India. A randomised controlled trial (RCT) is a study design that randomly assigns units (e.g. participants) to a treatment group or a control group, where the treatment consists of the real implementation of a policy or programme, and the control group serves as the counterfactual.