Q
I am putting a Control Chart together in excel and I am using the Chart in the manual as a reference. It is the first chart from appendix 1. As I was using this and several examples found elswhere I came to notice that the first subgroup does not calculate average or range in the SPC manual but all of my other examples do. What is the correct way to do this? I believe to get accurate control limits the first data should also be calculated. Am I missing something or is my cold medicine making me more of an airhead than usual?
Mark
Mark