6 sigma is a statistical toolbox designed to assist process improvement. It was originally developed by Motorola in the 80’s as they struggled with quality problems in their booming but now extinct mobile phone business. The tools seek to identify and remove the causes of variability and resulting defects in manufacturing processes. It uses statistics to identify problems, formulate remedial action, then track the impact of improvements as they are implemented.
In simple terms, 6 sigma compliance means there is less than 3.5 defects in a million opportunities for that defect to occur. This can apply to a specific machine or action, or whole production line. Clearly the latter creates many more opportunities for error, and therefore harder to stay ahead of the 3.5 defects/million opportunities benchmark.
Improvement projects are run to a proven statistical ‘recipe’ going by the acronym of DMAIC.
Define. Using statistics, define the problem, and the deliverables of the project.
Measure. By collecting data, you measure the ‘current state’ of the process or activity. This is the starting point from which the improvements will be measured.
Analyse. By analysing the data from each point of input, usually by experimentation, you isolate the cause-and-effect chains in the activity. This identifies the root causes of the variation being investigated.
Improve. Removal of the causes of variation will result in improved performance. The improvements require that changes be made and that the improved processes become the Standard Operating Procedures (SOP).
Control. Control is the continuing monitoring of the improved process to ensure that there is no ‘back-sliding’.
When engaged in a 6 sigma type project, I like to combine it with the SMART methodology in each component of the improvement process. This enables pro-active project management of the components of the process.
6 sigma is often confused or conflated with ‘Lean’ methodology. They use a similar toolset while coming at problems from different perspectives. In my view, and some disagree, they are highly complementary.
