Читать книгу Supply Chain Management For Dummies - Daniel Stanton - Страница 72

Six Sigma is a process improvement method that’s built on statistics. The basic idea is that variation is bad. When you’re running a manufacturing process or a supply chain, you need consistency and predictability. If you don’t have consistency, some percentage of the things that you make probably isn’t useful for your customers. If you do have consistency — that is, if you have a process under control — there’s a much better chance that the products you make are useful. Consistent processes lead to a high quality level for products.

Statisticians describe the variation of a process in terms of the amount of deviation from an average value. The symbol used to represent deviation in a mathematical equation is the Greek letter sigma (σ). Any set of data about a process has some deviation, and the less deviation you have, the more stable your process is. So the statistical basis for Six Sigma is to reduce process variability so much that defects occur only at the sixth sigma (6σ), or just 3.4 defects out of 1 million events.

I don’t want to get too deep into the math here; you can find plenty of other books that do. The important thing to understand about Six Sigma is that the goal is to have a very small number of defects — that is, improved quality — as a result of decreased process variation. You get there by measuring processes and using mathematical tools to improve consistency.

There’s so much overlap between Lean and Six Sigma that some people combine them into a single discipline called Lean Six Sigma.

You follow five steps to apply Six Sigma as a process improvement methodology. These steps create the acronym DMAIC (pronounced “duh-may-ick”).

 Define

 Measure

 Analyze

 Improve

 Control

Another Six Sigma approach called DMEDI (Define, Measure, Explore, Develop, Implement) is used to design new processes.