mber of defects in every sample is decreased.The second approach is to make improvements in the process itself so the chances of defects are lowered. That will reduce the value of the standard deviation, or sigma, of the process. If, say, the value of the sigma can be halved through this method to 0.005, the acceptable specification limits 99 07 mm and 100.03 mm, will automatically become 6 times and not 3 times the standard deviation. To take a process to a Six Sigma level, you must, ideally, adopt both approaches: changing the design to increase the range of acceptability in the CTQ, and improving the process to reduce its chances of variance.You can also expect your Six Sigma analysis to show up faults you were not even aware of Recalls Anand Outta, 40, President, GE Motors "We thought there was a bias against us when our parent began insisting on a Pareto rating of our products before shipment. But, when we quantified our defects using Six Sigma tools, we realized that we were generating 20,000 faults per million spares, and the faults weren't even major; most of them were just the results of carelessness." Adds V. Rama Kumar, 45, Corporate Vice-President, Wipro: "In addition to the quantitative gains, Six Sigma has helped us streamline our processes. That will help us in future too." Some may argue is 3.40 defects per million too high of a standard. Why isn't 6,210 (Three Sigma) defects per million parts, which is the upper end of the corporate average in the US not good enough? The average product rolling off your assembly lines today could consist of as many as 10,000 different parts, which all have risk of being defective. Therefore, 3.4 defects per million parts actually amount to 34 defective products out of every 1,000. In other words, an average of 34 out of 1,000 customers will still be unhappy about their product. In terms of quality of everyday life, Four Sigma would mean 1,24,200 wrong prescriptions a year, 4 60 hours o...
