ISO 9001 is a formal quality management system standard that defines requirements for how you manage and control processes, documents, and improvements. Six Sigma is a problem‑solving and process improvement methodology focused on reducing variation and defects. They are not interchangeable: ISO 9001 can be certified against, Six Sigma cannot. In regulated, brownfield plants they typically coexist, with ISO 9001 providing the governance framework and Six Sigma providing tools and projects within that framework. Benefits depend heavily on process maturity, data quality, leadership support, and disciplined change control.
