Six Sigma

 Six-Sigma: (definition):

The definition of the phrase “six sigma” is somewhat obscure.  People and organizations that have played key roles in encouraging others to use the phrase include the authors Harry and Schroeder (1999), Pande et al. (2000), and the American Society of Quality.  These groups have clarified that “six sigma” pertains to the attainment of desirable situations in which the fraction of unacceptable products produced by a system is less than 3.4 per million opportunities (PMO).


The definition of six sigma is built on the one offered in Linderman et al. (2003, p. 195). Writing in the prestigious Journal of Operations Management, those authors emphasized the need for a common definition of six sigma and proposed a definition paraphrased below:

“Six sigma is an organized and systematic problem-solving method for strategic system improvement and new product and service development that relies on statistical methods and the scientific method to make dramatic reductions in customer defined defect rates and/or improvements in key output variables. “

The authors further described that while “the name Six Sigma suggests a goal” of less than 3.4 unacceptable units PMO, they purposely did not include this principle in the definition. This followed because six sigma “advocates establishing goals based on customer requirements.” It is likely true that sufficient consensus exists to warrant the following additional specificity about the six sigma method:

The six sigma method for completed projects includes as its phases either-Define, Measure, Analyze, Improve, or Control (DMAIC) for system improvement or Define, Measure, Analyze, Design, and Verify (DMADV) for new system development.

Note that some authors use the term Design for Six Sigma (DFSS) to refer to the application of six-sigma to design new systems and emphasize the differences compared with system improvement activities.

Further, it is also probably true that sufficient consensus exists to include in the definition of six-sigma the following two principles:

Principle 1: The six sigma method only fully commences a project after establishing adequate monetary justification.

Principle 2: Practitioners applying six-sigma can and should benefit from applying statistical methods without the aid of statistical experts.

The above definition of six-sigma is not universally accepted.

a)      First, six sigmarelates to combining statistical methods and the scientific method to improve systems.

b)      Second, six sigmais fairly dogmatic in relation to the words associated with a formalized method to solve problems.

c)       Third, six sigmais very much about saving money and financial discipline.

d)      Fourth,there is an emphasis associated with six-sigma on training people to use statistical tools that will never be experts and may not come into contact with experts.

e)      Finally, six sigma focuseson the relatively narrow set of issues associated with technical methods for improving quantitative measures of identified subsystems in relatively short periods of time.

Many “softer” and philosophical issues about how to motivate people, inspire creativity, invoke the principles of design, or focus on the ideal end state of systems are not addressed.

Management Fad:


Example:What aspects of six-sigma suggest that it might not be another passing management fad?

Solution:Admittedly, six-sigma does share the characteristic of many fads in that it’s associated methods and principles do not derive from any clear, rigorous foundation or mathematical axioms.


Properties of six-sigma that suggest that it might be relevant for a long time include:

 (1)The method is relatively specific and therefore easy to implement, and

 (2)Six-sigma incorporates the principle of budget justification for each project. Therefore, participants appreciate its lack of ambiguity, and management appreciates the emphasis on the bottom line. Associated with six sigma is a training and certification process.

Other properties associated with six sigma training are:

1.Instruction is “case-based” such that all people being trained are directly applying what they are learning.

2.Multiple statistics, marketing, and optimization “component methods” are taught in the context of an improvement or “problem-solving” method involving five ordered “activities.” These activities are either “Define” (D), “Measure” (M), “Analyze” (A), “Improve” (I), and b“Control” (C) in that order (DMAIC) or “Define” (D), “Measure” (M), “Analyze” (A), “Design” (D), “Verify” (V) (DMADV).

3.An application process is employed in which people apply for training and/or projects based on the expected profit or return on investment from the project, and the profit is measured after the improvement system completes.

4.Training certification levels are specified as “Green Belt” (perhaps the majority of employees), “Black Belt” (project leaders and/or method experts), and “Master Black Belt” (training experts).