Abstract
Conformity assessment is making a decision about whether a product, service or other entity conforms to specifications. This final chapter deals with putting into use, when making decisions, all the measurement tools given in the intervening chapters to demonstrate to what extent actual measurement results live up to the initial motivations for making conformity assessment (providing consumer confidence; tools for supplier and supplier when ensuring product quality; essential for several reasons, such as health, environmental protection, fair trade and so on) presented in Sect. 1.1.
Quality assurance of product is intimately related, as said previously, to the quality of measurement—comparability of product quality characteristics is obtained by measuring product with comparable measurement, as assured by metrological traceability to agreed and common reference standards.
Measurement uncertainty leads to certain risks of incorrect decisions in conformity assessment. In this closing chapter, the predictions of design of experiment, ‘rules of thumb’ and more insightful judgements about ‘fit-for-purpose’ measurement and optimised uncertainty based on cost and impact, will be revisited with the actual measurement results in hand, such as obtained in the pre-packaged goods example followed throughout the book.
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Notes
- 1.
The factor ‘2.8’ approximates \( 2\bullet \sqrt{2} \) for the root-mean-square of the two results, multiplied by 2 to correspond to a 95% confidence interval (assuming a Normal distribution of the mean), as in the SDC expression Eq. (6.3).
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Exercises: Measurement and Product Decisions
Exercises: Measurement and Product Decisions
6.1.1 Conformity Assessment
Referring to your product and measurement demands as well as your measurement data (that you have specified in each section of this document) | Your answers………………………………………… |
|---|---|
(§1.2) What are the ‘optimal’ values of the product’s most important characteristics? | |
(§1.2) How large deviations from these optimum values can be tolerated? | |
(§1.2) How much will your costs vary with varying deviations in product characteristics? | |
(§2.2) Maximum permissible uncertainty (MPU)? | |
(§2.1) How much does the test cost? | |
What is the real ‘value’ (e.g. in economic or impact terms) of the measurement values? | |
(§4.2) From your measurement results | |
• Is your actual measurement uncertainty within measurement specification (i.e. MPU)? | |
• Is the test result (including uncertainty interval) within product specification (i.e. MPE) about the ‘optimum’ product value? Is the product approved or not? | |
• What is the real ‘value’ (e.g. in economic or impact terms) of the measurement values? | |
• Give the measurement uncertainty and test result location with respect to product specification limits; risks for erroneous decisions when assessing compliance (‘conformity assessment’). Express these preferably in terms of consumer and supplier risks, either in % or preferably in tangible terms (e.g. economy) | |
• Does the actual measurement uncertainty lie close to the ‘optimum’ uncertainty, i.e. after having balanced (§2.1) measurement and (§1.2) consequence costs? | |
When you communicate your results to the task assigner, what will be your final words? | |
Others: |
6.1.2 Significance Testing
Choose any measurement situation: It can be measurements of the product you have chosen | Your answers………………………………………… |
• Give an estimate of the precision (scatter) in your measurement method and explain how you have estimated this precision | |
Choose two individual measurement results from your measurement data | |
• Is the difference between these two results significant compared with the precision of the measurement method? Please give a confidence level (%) in your decision | |
Others: |
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Pendrill, L. (2019). Decisions About Product. In: Quality Assured Measurement. Springer Series in Measurement Science and Technology. Springer, Cham. https://doi.org/10.1007/978-3-030-28695-8_6
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