The suitability of estimating reliability of VAS and Numerical rating depends on the group of patients, there educational back ground, selected disease, tolerance of individual patient, their understanding, type of clinical trial, researcher etc.
Thank you Dr Gandhidas & Professor Muayyad Ahmad for answering my questions, While estimating test to retest reliability, how much the time difference is required between test and retest if i wanted to assess the post operative pain level of patients after Coronary Artery Bypass Graft Surgery using VAS?