(iv) Variation: The things that the customer witnesses and feels (v) Stable operations: Making sure consistent, predictable processes so as to improve what the customer is able to see and feel. (vi) Design for Six Sigma: Designing to fulfill the requirements of the customer and process capability. One of the most important aspects which companies fail to recognize is that assessment from the company level is based on average or averages that are based on mean of the latest results. However, customers do not judge companies on averages, they perceive the variance in every transactions and every product that is shipped. The main idea of Six Sigma remains primarily in reducing process variation and thereafter on improving the capability of processes. (Key concepts of Six Sigma) .

             A question that is usually put is the difference between Six Sigma and TQM. The tools are fundamentally identical based on the level of TQM sophistication. In case Six Sigma is applied exclusively at the project stages to eliminate flaws, it constitutes a segmental improvement approach with some structure and discipline. This can be extremely precious, however misses much of the real importance of Six Sigma and the crucial differences between TQM and Six Sigma. It is important that the real values of Six Sigma begins to exhibit when it is integrated with the strategic plan of the organization assisting to execute that plan with a concentration on paying the customers. (Differences and similarities between Six Sigma and TQM, total quality management) .

             Various Methodologies of Six Sigma: .

             (i) The DMAIC Model: Six Sigma originated in Motorola's quality enhancement initiatives in the later part of 1980s. During the 1990s, Six Sigma attained popularity due to the success of General Electric and Honeywell implementing Six Sigma. Whereas the name Six Sigma has assumed wider implications, the basic idea of Six Sigma statistically speaking is to enhance the processes in such a manner that at the minimum six standard deviations between the worst case specification limit and the mean of process variation is present.