Six Sigma
六西格玛
Nov 6th 2009
From Economist.com

A popular way for managers to put quality management into effect
管理者有效实施质量管理的途径

This is an approach to quality improvement based on the statistical work of Joseph Juran, one of two American pioneers of quality management in Japan. Sigma is a Greek letter used in mathematics to denote standard deviation, a statistical measure of the extent to which a series of numbers or readings deviates from its mean. One Sigma indicates a wide scattering of the readings. If the mean is the required quality standard of a particular process or product, then One Sigma quality is not very good. The higher the number, the closer the readings come to total perfection. At the Six Sigma level, there are only 3.4 defects per million.
这一方法是由约瑟夫•朱兰的统计结论发展而来，朱兰是将质量管理理念引入日本的两位先驱者中的一员。西格玛（σ）是一个希腊字母，表示数学里的标准差，即一系列数字偏离其均值的程度。一西格玛（σ）就表示这些产品（流程）的质量不如人意。西格玛（σ）的值越大，产品的合格率就越高。6西格玛（6σ）就表示次品率为3.4/100万。

This may sound complicated, but in practice it has proved a popular way for managers to put quality management into effect. One of its great advantages is that it eschews the idea of aiming for “zero defects”, or total perfection—a dauntingly inaccessible goal for most. It presents a system for improving quality gradually. Companies or operational groups move step-by-step up the Sigma ladder, the ultimate goal being to reach the Six Sigma state—still just short of perfection. Reasonably unsophisticated computer programs do the necessary calculations when fed with data on the goals (the specifications of the perfect product or process) and the organisation’s actual achievements.
乍听起来似乎有些晦涩难懂，但实践证明这的确是管理者施行质量管理的一种有效途径。这种方法有一个重要的特征就是它并非追求产品一次性达到零缺陷或全部合格的水平，因为这几乎是不可能实现的。它追求的是产品质量的逐步提高，企业循序渐进地提高产品的西格玛值，最终达到6西格玛（σ）的水平（但这也不代表所生产的产品全部合格）。他们将目标数据（合格产品的标准数据）和企业所生产出的产品的实际数据输入电脑程序，得出最终结果。

Six Sigma sounds like some sort of secret coven. Its advocates insist that it is no such thing. But it has certain attributes of the exclusive society. Anyone in an organisation who goes on a basic training course for a Six Sigma programme (and training is essential to an understanding of what it is about) is called a Green Belt. Anyone who is given the full-time job of leading a team that is embarking on a Six Sigma exercise is given further training and is called a Black Belt. Beyond this there are a special few who are trained even more, and they are called Master Black Belts. Their role is to champion the exercise throughout the organisation and to watch over the Black Belts and ensure that they are consistently improving the quality of their team’s output.
六西格玛（σ）听起来似乎有点神秘，而其推崇者则并不这样认为。但作为一个特殊的团体，它的确有上些独特的属性。企业内部那些接受过“6西格玛（σ）”基础培训（掌握“6σ”的基本内容）的人被称为绿带。而黑带因为要带领团队执行“6σ”项目，则需要接受更深层次的培训。除此之外还有极少一部分人需要接受进一步培训，他们被称为黑带大师，其主要职能就是为“6σ”项目在团队的实施提供技术支持，并指导黑带以使其不断提高其团队产品的质量。

In its annual report for the year 2000, chemicals giant DuPont reported:
Six Sigma implementation continues to gain momentum. At the end of the year, there were about 1,100 trained Black Belts and over 3,400 active projects. The potential pre-tax benefit from active projects was $700m.
化工业巨头杜帮公司在其2000年年报中指出：
公司的6σ项目的进展状况良好。至本年底，项目已培养出1100名黑带，并优化了超过3400项工程。这些工程为公司带来了700万美元的潜在税前利润。

Pioneered in the United States by Motorola in the 1980s (and registered by the company as its own trademark), Six Sigma became hugely popular in the 1990s after Jack Welch adopted it at General Electric. Mikel Harry and Richard Schroeder, the two men who introduced the method to Motorola, went on to set up the Six Sigma Academy, a consultancy which has worked with such companies as Allied Signal, GR and ABB.
“6σ”理论最早出现于20世纪80年代，由摩托罗拉公司开发（且该公司已注册了“6σ”的商标使用权），并在90年代由杰克•韦尔奇引入通用电汽（GE）后开始风行。将该理论应用到摩托罗拉公司的迈克尔•哈里以及理查德随后组织建立了“6σ协会”，为Allied Signal、GR和ABB等公司提供咨询服务。

To achieve Six Sigma quality at GE, a process must produce no more than 3.4 defects per million “opportunities”. An opportunity is defined as “a chance for non-conformance, or not meeting the required specifications”. The company says: “Six Sigma has changed the DNA of GE. It is now the way we work—in everything we do and in every product we design”.
GE要达到“6σ”的质量水平，就意味着它所生产的产品的“次品率”不得高于3.4/100万。这个概率是指“产品不满足标准要求的机率”。公司内部表示“6σ已经改变了GE的基因。不论做什么事、生产什么产品，它已经成为了我们的工作方式”

However, Six Sigma has not been an unmitigated success for everybody. Robert Nardelli took it with him when he moved from GE to head up Home Depot. But in August 2007 the Wall Street Journal reported that he had angered employees greatly with his attempt to force it upon them. Nardelli went on to try to resuscitate General Motors.
然而，6σ并非人人适用。罗伯特•纳德利当年离开GE到家得宝公司当“一把手”时，也在家得宝大力实施6σ项目。但2007年8月的华尔街日报的报道称纳德利强行在家得宝实施6σ项目已经惹恼了公司的员工。而现在纳德利又打算继续用这一方法来挽救通用汽车公司。