Since 1988, the International Committee of Medical Journal Editors has used this language in their guidelines for authors: “When possible, quantify findings and present them with appropriate indicators of measurement error or uncertainty (such as confidence intervals). Avoid relying solely on statistical hypothesis testing, such as the use of P values, which fails to convey important quantitative information.”1,2 Hundreds of biomedical journals, including the Archives,3 endorse these guidelines. What concerns do editors have about P values and hypothesis testing?