I work in a QC Microbiology lab for a CDMO. We have suffered from a historical lack of writing shit down when it comes to broader scope of things like "how to reevaluate alert and action limits" after doing annual report trending. So while our SOP says "reevaluate your limits" it does not give any guidance as to how to determine if those limits we set in our manufacturing facility need to change.

My colleague recalls using an equation that incorporates some statistics in a previous job but doesn't have access to those SOPs anymore to refer to. So my question I pose to you is this, how do you reevaluate your limits each year? Said colleague and I are working to improve our SOPs so that if we ever move on to other roles, that the people who follow us won't have the same struggle.