Design For Six Sigma (DFSS) can be seen as a theory that binds different areas of knowledge not necessarily engineering and that aspires to develop projects for new processes or products that are optimal in terms of full satisfaction of the end customer’s requirements.

The term “Six Sigma”, just as reflected in the well-known Lean Six Sigma methodology in the context of the improvement of existing processes and products, in the context of the DFSS is defined as the level at which so-called possible conceptual or operational product vulnerabilities also called Critical to Quality or Critical to Satisfaction (CTQ or CTS) are minimal at the project level (frequency of occurrence from 2 parts per billion to 3.4 parts per million depending on the type of process or product taken into consideration).

The DFSS in particular is based on particular project methodologies, such as Axiomatic Design and the Theory for the Inventive Solution of Problems (commonly identified with TRIZ), and on a broad spectrum of quantitative (eg Hypothesis Test) or qualitative statistical tools ( eg DFMEA) that allow, starting from evaluations also in the form of empirical measures and evaluations in the field of Customer requests (VOC, Voice Of the Customer) and prototypes or simulations of process or product through approaches such as Design Of Experiment (DOE) or the Taguchi Method, to create specimens that show that they are “correctly designed the first time”, making the possibility of returning to them small after being put into production. Therefore, the purely “proactive” approach of the DFSS against the “reactive” (firefighting) approach not methodologically structured in the design remains clear.