wht is six sigma ??

Six Sigma was originally developed as a set of practices designed to improve manufacturing processes and eliminate defects, but its application was subsequently extended to other types of business processes as well.^[2] In Six Sigma, a defect is defined as anything that could lead to customer dissatisfaction.^[1]

The particulars of the methodology were first formulated by Bill Smith at Motorola in 1986.^[3] Six Sigma was heavily inspired by six preceding decades of quality improvement methodologies such as quality control, TQM, and Zero Defects,^[4]^[5] based on the work of pioneers such as Shewhart, Deming, Juran, Ishikawa, Taguchi and others.

Like its predecessors, Six Sigma asserts that –

Continuous efforts to achieve stable and predictable process results (i.e. reduce process variation) are of vital importance to business success.
Manufacturing and business processes have characteristics that can be measured, analyzed, improved and controlled.
Achieving sustained quality improvement requires commitment from the entire organization, particularly from top-level management.

Features that set Six Sigma apart from previous quality improvement initiatives include –

A clear focus on achieving measurable and quantifiable financial returns from any Six Sigma project.^[1]
An increased emphasis on strong and passionate management leadership and support.^[1]
A special infrastructure of "Champions," "Master Black Belts," "Black Belts," etc. to lead and implement the Six Sigma approach.^[1]
A clear commitment to making decisions on the basis of verifiable data, rather than assumptions and guesswork.^[1]

The term "Six Sigma" is derived from a field of statistics known as process capability studies. Originally, it referred to the ability of manufacturing processes to produce a very high proportion of output within specification. Processes that operate with "six sigma quality" over the short term are assumed to produce long-term defect levels below 3.4 defects per million opportunities (DPMO).^[6]^[7] Six Sigma's implicit goal is to improve all processes to that level of quality or better.

Six Sigma is a registered service mark and trademark of Motorola, Inc.^[8] Motorola has reported over US$17 billion in savings^[9] from Six Sigma as of 2006.

Other early adopters of Six Sigma who achieved well-publicized success include Honeywell (previously known as AlliedSignal) and General Electric, where the method was introduced by Jack Welch.^[10] By the late 1990s, about two-thirds of the Fortune 500 organizations had begun Six Sigma initiatives with the aim of reducing costs and improving quality.^[11]

In recent years, Six Sigma has sometimes been combined with lean manufacturing to yield a methodology named Lean Six Sigma.