With the availability of limited resources, innovation for improved statistical method for the design and analysis of randomized controlled trials are of paramount importance for newer and better treatment discovery for any therapeutic area. Although clinical efficacy is almost always the primary evaluating criteria to measure any bene?cial effect of a treatment, there are several important other factors, which can permit some less efficacious treatment options favorable to a subgroup of patients. This leads to non-inferiority (NI) testing. The objective of NI trial is to show that an experimental treatment is not worse than an active reference treatment by more than a pre-speci?ed margin. Traditional NI trials do not include a placebo arm for ethical reason. Three-arm NI trials consisting of placebo, reference, and experimental treatment, can simultaneously test the superiority of the reference over placebo and NI of experimental treatment over the reference. In this paper, we consider both Frequentist and Bayesian procedure. . In addition, we discuss sample size calculation and draw an interesting connection between the two paradigms.