Criticisms of 6 Sigma

May.19, 2009 in 6 Sigma

Criticisms of 6 Sigma

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6 Sigma is controversial with the statistics profession. Some teachers of statistics are critical of the standard of statistical teaching found in 6 Sigma materials. Others object to the idea that a single universal standard can be appropriate across all domains of application. They argue that quality standards should be set on a case-by-case basis using decision theory or cost-benefit analysis.

Others suggest that 6 Sigma, rather than being a true methodology, is more often implemented to start an unending cycle of improvement and use of better tools on the industry day to day practices rather than to use advanced statistical theories that cannot be daily applied.

Basic 6 Sigma methodologies

6 Sigma DMAIC
Basic 6 Sigma methodology to improve existing processes

Define - formally how much the process need to improve, potential savings, boundaries, objectives.
Measure - to define baseline measurements on current process for future comparison and better understanding of current performance.
Analyze - to find and prove relationship between potential root causes and its effects (y=f(x)).
Improve - process through proposition of improvements, testing and full implementation.
Control - the causes (Xs) and monitor the effects (Ys) in order to maintain the gains.

6 Sigma DMADV
Basic 6 Sigma methodology to improve existing processes

Define - formally how much the process need to improve, potential savings, boundaries, objectives.
Measure - to define baseline measurements on current process for future comparison and better understanding of current performance.
Analyze - to find and prove relationship between potential root causes and its effects (y=f(x)).
Design - the process to meet the customer needs.
Verify - the design performance and ability to meet customer needs.

6 Sigma Training
There are two levels of training in the 6 Sigma quality system - Black Belts and Green Belts.

6 Sigma Black Belts are basically the on-site 6 Sigma implementation experts who will develop, coach and lead cross-functional teams, mentor and advise management on prioritising, planning and launching

6 Sigma projects. In short, they are the ones who will be directly responsible for the execution of projects in a 6 Sigma organisation. They are expected to take on projects with projected savings of US$200K.

6 Sigma Green Belts are employees throughout the organization who execute 6 sigma as part of their overall jobs.
They have less 6 sigma responsibility and their energies are focused on projects that tie directly to their day-to-day work. 6 Sigma Green Belts have two primary tasks: first, to help deploy the success of 6 sigma techniques, and second, to lead small-scale improvement projects within their respective areas.

6 Sigma Green Belts can do much of the legwork in gathering data and executing
experiments in support of a 6 Sigma Black Belt project.