ident, GE Capital Asia:"In a services company, you measure your output. A courier company carries so many parcels, and you say so many of them reached on time. What Six Sigma does is to allow you an efficient way of finding out where your greatest need is and what your softest point is, and of addressing them in a measurable, analytical, and objective way."The mathematical interpretation of Six Sigma is crucial to implementing the tool. The output of any process in your company can be analyzed in terms of the number of errors in it. What Six Sigma analysis does is to measure every process on each of the CTQ factors. For example, a process that produces 100 units of a particular component every hour has a CTQ of 100 mm in length. Measurements may show that while 95 out of the 100 units produced are 100-mm long. The remaining 5 deviate from that ideal length, each to a different extent This data can be used to calculate the sigma, or the likelihood and extent of deviations from the norm of the process. Assume that the value of sigma for this process turns out to be 0.01.The upper and lower specification limits of the product will determine whether these deviations will be counted as flaws under the given CTQ. If the upper and lower control limits of the process fall beyond the upper and lower specification levels, the customer won't have a problem, but if they do not the capability of the process has to be changed.Six Sigma offers two approaches to changing a process. One approach is to change the design of the product in which this component is used so that it can accommodate some of the variations in the length without malfunctioning. Thus, for instance, the so-called design-length could be three sigma, accommodating components with 3 times the standard deviation of the process. In other words, components that measure between 99.07 mm and 100.03 mm will also be acceptable. Units that exceed three sigma are still eliminated, but the nu...
