When should a technician not rely on selective sampling?

A technician should not rely on selective sampling to isolate non-specification materials because selective sampling may not provide a comprehensive picture of the entire material batch. Selective sampling involves choosing specific portions of material to test, which can introduce bias and may overlook areas that do not meet specifications. When the goal is to identify and isolate materials that do not meet quality standards, a more representative and random sampling method is necessary to ensure that all potential issues are identified. This approach minimizes the risk of missing critical defects or inconsistencies across the entire batch.

In contrast, during production, verifying performance, or post-production assessments, selective sampling may be suitable under certain conditions, assuming that the technician employs it carefully and with an understanding of its limitations. However, when the objective is specifically to isolate non-specification materials, relying solely on selective sampling can compromise the integrity of the quality assurance process.