# Come interpretare correttamente il valore di P?

### AUTORI

Azienda Ospedaliera Universitaria Integrata di Verona

### ABSTRACT

#### Understanding the P value

A number of recent contributions about the P value in statistics gave the spur to consider different aspects of its use in scientific papers. There is indeed a need of correct information on how and when to apply the P value to evaluate results of a scientific experiment and how to appropriately interpret the numerical value as well, considering that the P statistic is rather frequently reported in the medical literature. In this paper we first described the origin of the P value and its correct significance, using examples where the statistical significance of the P value does not necessarily mean a clinical significance. Then, we defined which kind of assumptions cannot be drawn from the a P value. The most common misuse is when a non-statistically significant P value is used to establish that two laboratory techniques are equivalent. Finally, some alternatives are given, the most common being the use of the confidence intervals. In spite of the interpretation mistakes commonly observed in scientific articles, the P value remains a useful statistic tool to be utilized and interpreted with better consciousness.