4. Declaration of conformity and uncertainty of measurement

4.1 Relationship between tolerance and uncertainty

Measurement results are used to declare conformity with specifications. Since all measurement results are subject to doubt or uncertainty, the decisions taken are not certain and carry a risk: the risk of declaring a product to be compliant when it is not, and conversely, the risk of rejecting a compliant product. This situation is inescapable, but industrial life is made up of decisions taken in the face of doubt, and as far as possible we must try to assess the risks taken.

The situation can be summarized on the figure 5 :

• in zone 1 conformity is declared;

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