The big picture
The name six sigma originates from statistical terminology. Sigma is the mathematical symbol for standard deviation. Six sigma is a measure of the maximum number of defects that are allowed in a system. At the six sigma level, 99.999998 per cent of all products must be good, i.e. they fall within the tolerance limits. This implies that no more than 3.4 defects are produced in one million opportunities. This level can be achieved by reducing the variation of the process and controlling it. To reach this quality level, the processes must be improved. However, process and quality improvements are not the ultimate ...