Experimental Study Design

This chapter discusses experimental study design. The research subjects in experimental studies can be randomly allocated to different treatment groups, and ideally, the conditions other than the treatment of interest between groups are controlled to examine a causal effect of the treatment. Applied to different biomedical research fields, experimental studies are divided into the following broad categories: laboratory experiments, clinical trials, and community intervention trial. There are three indispensable elements in experimental studies: research subjects, treatment factors, and experimental effects. The chapter introduces several common concurrent controls: placebo concurrent control, active treatment concurrent control, historical control, and self‐control. It introduces the most common experimental design: completely randomized design. A factorial design has an advantage in detecting potential interaction effects between interventions. A crossover design is more ethically attractive compared with a completely randomized because all patients have the opportunity to receive both treatments.