According to the authors Ikel Harry, Ph.D., and Richard Schroeder in the fifth chapter of their book SIx Sigma: The Breakthrough Management Strategy Revolutionizing the World’s Top Corporations, Six Sigma is a tool for changing the processes that companies use to create their products or services in order to improve their quality.
However, there is two caveats to this statement. In order to change a process, you have to be able to measure it. Also, improving quality does not mean getting rid of defects. A defect-free product which a customer does not want is not going to be sold. So what companies need to do is measure their customer’s opinions, and then to link those measurements of the customer’s requirements to a company’s processes.
How do companies fail at this central task? Some don’t measure quality accurately in the sense of quantitatively capturing their customer’s opinions. Some take these measurements of quality but don’t follow them up to make sure that the customer’s requirements are linked to a company’s processes. Some fail to describe their processes in terms of numbers, rather than words.
The author’s basic credo (listed in italics in the first paragraph) has a negative corollary: if you don’t understand your processes quantitatively, you can’t control them. These processes have to be correlated with a customer’s opinions, as mentioned above, but they also have to be correlated with the company’s fundamental economics. This is the only way to make sure that a company’s business case for producing the product is solid.
How are processes described quantitatively? By the use of metrics, which are discussed in the next post.