Introduction to Six Sigma
Six Sigma is a statistical concept that measures a process in terms of defects. Achieving “Six Sigma” means your processes are delivering only 3.4 defects per million opportunities (DPMO) – in other words, they are working nearly perfectly. Sigma (the Greek letter σ) is a term in statistics that measures standard deviation. In its business use, it indicates defects in the outputs of a process, and helps us to understand how far the process deviates from perfection.
A sigma represents 691462.5 defects per million opportunities, which translates to only 30.854% of non-defective outputs. That is obviously a poor performing process. If you have a process functioning at a three sigma level that means you’re allowing 66807.2 errors per million opportunities, or delivering 93.319% non-defective outputs. That’s much better, but we are still wasting money and disappointing our customers.
The central idea of Six Sigma management is that if you can measure the defects in a process, you can systematically figure out ways to eliminate them to approach a quality level of zero defects.
In short, Six Sigma is several things:
- A statistical basis of measurement: 3.4 defects per million opportunities
- A philosophy and a goal: as perfect as practically possible
- A methodology
- A symbol of quality