ELENA PASQUALI
PRINEOS srl, Milano, Italy

INTRODUCTION
In the first article of this column, privacy compliance has been thoroughly examined as a fundamental part in clinical trials’ challenges.

Another important aspect of clinical research methodology being critical for the success of a trial is definitely sample size calculation. Sample size should be properly calculated at the very beginning of any epidemiological or clinical study, since it is a crucial step in the design of a study from several points of view, including methodological, ethical, and financial perspectives.

The present article provides the key components and statistical assumptions for calculating an adequate sample size and explains the reasons why a proper sample size calculation is crucial for a clinical research to be successful.

WHAT IS THE SAMPLE SIZE?
Sample size is the number of individuals that need to be included in a study or experiment investigating any treatment in order to be able to detect a clinically relevant treatment effect (i.e., a treatment outcome that generally physicians would identify as important).

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