A p value is simply a probability. However, it is a conditional probability, in that its calculation is based on an assumption (condition) that the null hypothesis (H0) is true. This is the most critical concept to keep in mind as it means that one cannot infer from the p value whether H0 is true or false. More specifically, after we assume H0 is true, the p value only gives us the probability that, simply owing to the chance selection of patients from the larger (target) population, the clinical experiment resulted in a difference in the samples.
(Dorey F. The p value: what is it and what does it tell you? Clin Orthop Relat Res. 2010 Aug;468(8):2297-8. doi: 10.1007/s11999-010-1402-9. PMID: 20499291; PMCID: PMC2895822.). (Alliance Glossary, June 2026)