(西格玛是.pptVIP

Three Schools of Quality Management Programs 西格玛（Sigma）是什么？ 西格玛是对质量好坏的度量：某一过程提供的产品或服务完美无缺的程度。 西格玛特指某个产品或某项服务在运作过程中的完善程度。 换言之： 在高西格玛水平上运行可以缩短运转周期 并达到顾客完全满意。 假设我们的生产过程中其中一个工序是将金属材料切割成每个长度为10mm的产品。当我们完成切割1000个产品后，测量每个产品的长度，并将测量结果以直方图形式表达，我们将会得到下列结果：:   Motorola 6-sigma 绩效--过去12年 平均每年生产力提高 12.3% 降低品质不良成本超过 84% 消除99.7%制程不良 节省制造成本超过110亿美金 实现综合收益增长平均每年17% 质量成本–为什么选择 6 Sigma?-1 END * * Start with the example of time to office Case A: Mean= 15 min.; +3 sigma = 55 min Case B: Mean= 25 min. +3 sigma = 30 min For example: Consider your drive to work. If you were to gather data over several weeks or months on how long it takes you to drive to work, you could plot these points and form a histogram. You could overlay a “normal” curve on this as an approximation of the distribution. The standard deviation (the point of inflection) of this curve is then a measure of the amount of variation (we’ll see the formula later). Is there a lot of variation for you? How do you know? How do you plan your schedule to accommodate that? What if there was little variation? Could you leave later? We define 3 sigma as being able to fit 3 standard deviations between specification limit and the average. With reduced variation, the standard deviation gets smaller and we can fit more standard deviations between the spec limit and mean. This actual standard deviation has a value dependent on the process data. The number in front the the sigma symbol is called Z. We often refer to it as sigma, as in “what’s your process’ sigma?” This sometimes can create confusion, but should be clear by the end of this session. For example: Consider your drive to work. If you were to gather data over several weeks or months on how long it takes you to drive to work, you could plot these points and form a histogram. You could overlay a “normal” curve on this as an approximation of the distribution. The standard deviation (the point of inflection) of this curve is then a measure of the amoun