In clinical research, a hypothesis is a specific, testable assumption regarding the effect of an intervention, formulated before the start of the study. It serves as the scientific foundation for every clinical trial. A distinction is typically made between the null hypothesis (H0) and the alternative hypothesis (H1).
The null hypothesis states that there is no difference between the treatment groups (e.g., ‘The new drug has the same effect as the placebo’). The alternative hypothesis states the opposite—that a difference does exist. The goal of statistical analysis is to gather sufficient evidence to reject the null hypothesis, thereby supporting the alternative hypothesis. Precise formulation of the hypothesis in the clinical trial protocol is crucial, as it directly influences the choice of study design, endpoints, and statistical methods. CRO biostatisticians assist in translating clinical questions into testable statistical hypotheses.