8. Notes on sample testing

To be properly representative, sampling requires a great deal of rigor.

• When inspection is carried out as part of a contract between manufacturers, and a non-conformity rate is specified, the supplier must not withdraw any parts found to be defective during inspection. Otherwise, the quality of the sample will no longer be representative of that of the batch, and the quality of the batch will itself have changed. Nor should the customer risk using parts found to be defective during inspection. The acceptance protocol must address these issues.

• Some samplings are particularly delicate: this is the case, for example, when there is a risk of disturbing the phenomenon to be studied. A typical example is sampling from a fluid or liquid containing solid particles in suspension. These cases,...