What exactly is six sigma?

Sigma (σ) is the Greek letter associated with standard deviation. However, in six sigma it takes on various definitions and interpretations, such as, a metric of comparison, a benchmark comparison, a vision, a philosophy, a methodological approach, a symbol, a specific value, or a goal. All of these present the holistic definition of what six sigma can do, but none of them accurately depict what six sigma really means. This convoluted explanation has contributed to the confusion of a standard definition, and that is why there are so many different interpretations.

In simple terms, six sigma engages each employee of the organization from the top executive to the employee on the manufacturing or service floor. It focuses on quality improvement, cost reduction, cycle time reduction and improved delivery performance. This results in higher profits and customer satisfaction. It also improves the relationship between the management and employees. Consistency of quality at all levels of the organization is easy through the use of common metrics that compare the quality of both technical and transactional processes. In addition, this powerful approach to improvement focuses on critical to customer (CTC) characteristics. The CTC is the first step of understanding in pursuing the six sigma methodology. It all starts with the functionality that the customer is seeking from either a product or a service. The more we understand this functionality (the Y in the six sigma equation Y = f(x), which is discussed later in this chapter), the more accurate will be our focus on the variables that control this functionality (the F(x)). However, we must not forget that this methodology is an approach that has borrowed many systems, tools and best practices from previous approaches and has combined them in a bundle called six sigma. It is precisely this bundle of tools and methodologies, in addition to the management commitment and overall attitude change, that has contributed to why the six sigma approach may be applied to every process in any organization.

Finally, six sigma integrates technology, company assets, management and employees with continual improvement practices such as:

• Project management.

• Team problem-solving.

• Statistical process control.

• Measurement system assessment.

• Process FMEA (Failure Mode and Effect Analysis).

• Mistake-proofing.

• Team-building.

• Applied statistics.

• Design of experiments.

• Cost of quality.

• Process mapping.

• Product reliability and other disciplines.