A preliminary step when planning a randomized clinical trial (RCT) is the sample size calculation. This is the determination of the optimal number of patients which ensures an adequate power to the study to detect as statistically significant a certain between-arms difference, if any, in the frequency/magnitude of a specific endpoint. The sample size calculation is performed by specific calculators requiring as input variables the expected effect size, the alpha error (α), the beta error (β) and the allocation ratio, this latter being the ratio between the number of participants allocated to the arms of a RCT. Herein, we provide a series of examples of sample size calculation in the context of superiority RCTs in elderly.
Keywords: Alpha error; Beta error; RCT; Randomized clinical trial; Sample size calculation; Study power.