To “P” or not to “P”, that is the question: A narrative review on P value

Abstract

Best medicine practice is thought to be based on evidence. Inferential statistics allow us to establish the strength of evidence in favor of or against a new research finding. The P value has been considered a reliable universal marker indicative of statistical significance of a study, thus driving the majority of practice-changing developments. Of late, the reign of the P value has been increasingly challenged by failure of replication of results in successive studies necessitating withdrawals of drug approvals. For the purpose of this narrative review, we performed a detailed literature search to identify relevant articles from the PubMed database and Cochrane library. We aimed to evaluate the drawbacks of the utilization of P value in a dichotomous way around a fixed cut-off of 0.05. Our review suggests that the P value must be interpreted as a continuum with smaller values depicting greater significance. The possible substitutes for P value are also discussed to enable a rational interpretation of results of new discoveries.