 The Cosmin checklist was developed through an international Delphi process involving 43 experts from various fields. It provides guidance on how to assess the quality of research related to patient reported outcomes, pros. This paper explains the panel's decisions regarding the design requirements and preferred statistical methods for which there is limited evidence in the literature or where the panel had extensive discussions. The topics covered include internal consistency, content validity, hypothesis testing, criterion validity, and responsiveness. The authors hope that this paper will help to increase the acceptance and use of the Cosmin checklist. This article was authored by Patrick Donald L, Alonso Giordi, Stratford Paul W, and others.