Six Sigma methodology can be defined as a series of systems of metrics that are used to measure defects and improve the quality of the processes by reducing the defect level to 3.4 in a million opportunities. Motorola was the first corporation to invent and implement Six Sigma in their business and saved $17 billion.

The Central Theme

It is generally observed that customers judge a product by what benefits they get out of using that particular product. So it can be safely said that overall customer satisfaction rests heavily on the consistency of the product. And to achieve this, there has to be a combination of improved process capability and reduced process variation.

As it has been mentioned, Six Sigma mainly concentrates on defects and process variation - so now let's find out more about defects. Defects are measured by a standard metric known as DPMO (defects per million opportunities) and they can be explained as being offset from the standard process. While evaluating the defects, the Six Sigma team should know that everything is quantifiable and that the basic measurable dimensions are time/delivery, quality, cost/price etc. In 6 Sigma jargon, these dimensions are known as Critical to Delivery, Critical to Quality and Critical to Price, respectively. Each of these dimensions has different significance to different industries in some way or the other and they need to be identified before commencing with Six Sigma implementation.

One of the most important concepts of Six Sigma is the measurement system. It is a well-known fact that a little bit of subjectivity creeps up in all measurement processes due to different capacity and capability level. For instance, some athletes are considered better than others, even when the performance evaluation criteria for everyone is same. It is this way because first human performance levels differ and also because in a group of observers no two observers will evaluate two performers in the same way because of their different mindsets. Thus, we can conclude that an individual's passing and failing is subjective and that there are gaps in the measurement system. It is noticeable that companies also share the same relationship with the customers.

The next Six Sigma concept is the variation in process or process variability. Process variability and defects are inter-linked and it can be said that the more is the process variation the bigger the probability of the occurrence of defects is. On the surface, this may not seem such a big threat but in reality, it is a lot more than can be anticipated. For instance, a truck transporting a 5-ton load to a distance of 10 miles takes 40 minutes will deliver 99.9997% defect free if supervised by Six Sigma; on the contrary, if four sigma is implemented then the same truck with same load will take 45 minutes. Although this may seem a small deviation, the defect free level comes down to 99.94% which is a good 20% defect that is being passed on to customers.

The core concept of Six Sigma concentrates on improving the existing methodology and creates a new defect-free strategy for production. This designing of defect-free methodology is done using DMAIC (define, measure, analyze, improve and control performances). The design is known as DFSS design for Six Sigma principles and it is implemented and supervised by Green and Black Belt professionals.