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Tham khảo tài liệu 'automotive quality systems handbook episode 15', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Chapter 20 Statistical techniques Scope of requirements Statistical techniques can be used for a variety of reasons from sampling product on receipt to market analysis. Any technique that uses statistical theory to reveal information is a statistical technique but not all applications of statistics are governed by the requirements of this part of the standard. Techniques such as Pareto Analysis and cause and effect diagrams are regarded as statistical techniques in ISO 9000-2 and although numerical data is used there is no probability theory involved. These techniques are used for problem solving not for making product acceptance decisions. The only statistical techniques which need control are those used to determine the acceptability of a product or service or the capability of a process that produces the product or service. Any activity where you rely on statistical evidence rather than physical measurement is an activity which should be governed by these requirements. The use of recognized techniques is important to the confidence one has in the result. It is similar to the use of measuring equipment that has been calibrated against known standards of accuracy. Unless you actually check every product measure every attribute or variable you cannot be 100 certain. But that is costly and you can be 99.99 certain by using statistical techniques 99.99 may be sufficiently accurate for your needs. The requirement may not apply to all product acceptance decisions. If your acceptance of the end product does not depend upon acceptance decisions being made on its component parts any sampling carried out on receipt inspection or in-process is not important to the product acceptance decision and can therefore be ignored in your documented quality system. This is a wise course of action if you can be sure this will always be the case but if you can t and more often than not you won t know it is prudent to encompass all sampling activities in your quality system. 548 .
