By and large, customers don’t judge a product by averages like performance but by what they actually get out of each product. Overall customer satisfaction rests heavily on the consistency with which the products are delivered.  This is a result of the combination of reduced process variation and improved process capability.

The Core Concept Of Six Sigma

Today Six Sigma core concepts concentrate around defects and process variations. Defects are measured by metrics known as DPMO, defects per million opportunities. We can think of defects as offsets from the standard. Nothing is subjective, as all parameters are quantifiable. Basic measurable dimensions include time/delivery, cost/price, quality etc. In industry jargon these are called Critical to Delivery (CTD), Critical to Price (CTP) and Critical to Quality (CTQ), respectively. Each of these has a different significance to different industries, which needs to be identified before embarking on Six Sigma implementation.

What comes under the microscope next is the measurement system. Common sense tells us that a little element of subjectivity is present in all man-made measurements. For example, the some singers may be marginally better than others.  A group of observers will score each singer a little differently, even if standards for performance have been established. Thus the criteria for an individual’s passing or failing is purely subjective, exposing the chinks in the measurement system.  It is this way with companies’ relationships with customers as well.

Process Variability is the second Six Sigma core concept.  The more variability in a process the larger the probability for a defect somewhere.  At the heart of this concept is elimination of variation of process for defect removal. For example, if a carriage takes 40 minutes to transport a 5-ton load a distance of 10 miles at 99.9997% defect free Six Sigma, a four sigma will take 45 minutes to cover the same distance per same load but at 99.94% defect free. It might appear that 99.94% is quite good – if this is your conclusion, you will need to think again.  Taking Six Sigma concepts into account, this equals a 20% defect in the product, which passes on to the customer.

The concept of Six Sigma is to improve the existing methodology or create a new, defect- free methodology for production. This is achieved through a methodology known as DMAIC, which is an acronym for Define opportunities, Measure performance, Analyze opportunity, Improve performance, Control performance.  DFSS is the design for Six Sigma principles. Black and green belts evaluate the whole system and various fixes are chosen to be implemented.