If you can measure, you can correct
The 6 sigma method offers various techniques and tools in order to drastically improve the processes capability while reducing defaults. The method aims for absolute regularity, indeed variability is a dissatisfaction source for customers.
If you can correct, you can also improve
Your clients will expect from you a product with a certain level of quality, following an accurate standard. Not being able to guarantee the quality of your whole production (that is to say not following the standards) represents heavy costs for your company. Variability of final quality is actually the consequence of the components instability which were already here during the production process, the lack of exactness for workers and more generally the complexity of the whole process. The 6 sigma approach offers to respect the limits by applying this principle:
"If you can measure how many defects you have in a process, you can systematically figure out how to eliminate them and get as close to zero defects as possible."
In the end, 6 sigma allows less than 3.4 defaults per million of produced unities or services.
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