Clinical interpretation of statistical significance

In any clinical study which compares versus an established therapy, the results will be expressed in terms of statistical significance. For this reason, it is important that every clinician interested in a judicious interpretation of the scientific literature, understands the origin and interpretation of statistical significance. The present paper addresses physicians attempting to give practical meaning to research results by discriminative and critical reading. The main aim is to explain in a simple way the meaning of the P-value, confidence intervals, and the required number to treat. Using practical examples, the most common mistakes in the interpretation of statistical significance are analyzed. The difference between statistical and clinical significance is emphasized and a new way to express and compare the practical utility of clinical trial results and the required number to treat is given.