Books and Articles by Neil DeCarlo

You don’t have to wait until your multi-vari data are collected to start creating the multi-vari chart for Six Sigma. Instead, you can build the chart, incrementally, adding more to it as you collect more data.Multi-vari charts can be drawn by hand; in fact, the process operators themselves can create them, providing those folks with a critical opportunity to invest themselves in the discovery of the root cause and the development of the solution.

To apply Six Sigma to your business and produce the best results, you need to understand what Six Sigma is, the principles of Six Sigma, and the DMAIC problem-solving method. The correct tools and use of the Six Sigma scale and methods will keep your data dependable and reusable.What is Six Sigma?Generally, Six Sigma is a set of techniques and tools that help businesses improve their processes.

In Six Sigma, you make progress the old-fashioned way — one project at a time. In essence, projects are the unit of change; they define the collective effort by which most Six Sigma progress is accomplished. Projects represent — and in fact are — the level of granularity expressed to manage Six Sigma change, from a single process improvement to a large-scale business improvement effort.

A cause-and-effect matrix — sometimes called a C&E matrix for short — helps you discover which factors affect the outcomes of your Six Sigma initiative. It provides a way of mapping out how value is transmitted from the input factors of your system (the Xs) to the process or product outputs (the Ys). With these relationships visible and quantified, you can readily discover the most-influential factors contributing to value.

For Six Sigma, 5S can be invaluable for reducing waste. High-performing processes and workplaces are always characterized by organization and cleanliness. The whole point is to reduce or keep out waste, and the method that helps you with that is called 5S. The process behind 5S began decades ago in Japan as a means of immediately engaging frontline process teams in the daily work of improvement.

The primary Statistical Process Control (SPC) tool for Six Sigma initiatives is the control chart — a graphical tracking of a process input or an output over time. In the control chart, these tracked measurements are visually compared to decision limits calculated from probabilities of the actual process performance.

From a quality perspective, Six Sigma is defined as 3.4 defects per million opportunities. This figure is called a Six Sigma level of quality. Sigma scores are thrown about so much that you definitely need to be comfortable understanding what they are and how they’re calculated. Basically, a sigma score tells you how many standard deviations can fit between the mean and specification limit of any process or specification.

FMEA can be very valuable for identifying failure modes in a Six Sigma Initiative. After scoring the severity of the possible effects, your cross-functional FMEA team brainstorms potential causes of the identified failure mode. Think of causes for the failure mode, not for the effect. In the pizza example, you need to think of causes for why the phone is answered on or after the fifth ring, not causes for why a customer hangs up or why a customer becomes disgruntled.

You must collect data for control charts for Six Sigma projects in a way that avoids a distorted or inaccurate view of the process performance — whether overly optimistic or too bleak. Using rational subgroups is a common way to assure that this distortion doesn’t happen. A rational subgroup is a small set of measurements in which all the items in the subgroup are produced under as similar conditions as possible, typically within a relatively short time period — short enough that special causes are unlikely to occur within the subgroup.