We don’t have control, we have choices. The best we can do is improve our method of making choices and hope for good results.
Typically, the most suspect processes or process steps for introducing variation are manual or judgment oriented in nature. For example, if an individual applies personal judgment within a process you would expect to see bias or higher variation in the process output. Automated processes will typically have more consistent performance and lower variation.
One of the best ways to find these manual or judgment steps in a process is through the use of a process map. As a process is mapped, decision points are represented as diamonds. This becomes the first place to look for variation.
First, remember that not all variation is bad. Planned variation, like that in an experiment, is a process improvement strategy. Unplanned variation, on the other hand, is nearly always bad.
Two types of variation concern a process improvement team. These are common cause and special cause variation. All processes will have common cause variation. This variation is a normal part of the process (noise). It demonstrates the process’ true capability. Special cause variation on the other hand is not normal to the process. It is the result of exceptions in the process’ environment or inputs.
Not all business problems lend themselves to the Six Sigma process improvement methodologies, especially those that have short time lines. There are many problems that business leadership understand and should just fix. A Six Sigma improvement project typically requires one to six months for a team to complete, depending upon the complexity and scope of the problem. This is longer than acceptable for some problems. In addition, many of the tools used in Six Sigma do not apply well to problems that are not process based. Examples of these would be emergencies and relationship issues. Process improvement tools apply better to up-front planning for these situations, than to the situations themselves.