Six Sigma as a Measure
Strictly speaking, Six Sigma is a measure of quality quoted as a sigma level. Hence we can talk about a 4-sigma product or a 3.2-sigma process. However, unlike many previous measures of quality (e.g. ISO 9000 or EFQM Business Excellence Model), it is universal and absolute. The measure can be used throughout an organisation. It applies equally to measuring the quality of an accounting process as it does to measuring product quality.
ISO 9000 or EFQM Business Excellence Model are both 'measures' of quality but they do not actually measure the quality of the product or service received by the customer. An organisation that has ISO 9000 and/or a high BEM score can still be delivering a product or service with many defects.
The Sigma Level relates to the performance level in Defects Per Million Opportunities or DPMO.
