Which description best differentiates random sampling from targeted sampling in product testing, and when is each appropriate?

• A. Random sampling is used only after nonconformities are found.
• B. Random sampling tests only one unit per lot.
• C. Random sampling selects units across lots for general quality assessment; targeted sampling focuses on suspected or high-risk areas or prior nonconformities.
• D. Targeted sampling randomizes across all units.

Answer: (C)

Sampling strategy in product testing is about how units are chosen to assess quality. Random sampling selects units across multiple lots in a way that gives each unit an equal chance, providing a general, representative view of overall quality and helping to estimate defect rates for broad quality assessment. Targeted sampling concentrates testing on suspected problem areas, high‑risk processes, or places with prior nonconformities, making the effort more efficient for verifying corrective actions or investigating specific issues. Each approach fits different situations: use random sampling when you want an unbiased view of overall performance across lots, and use targeted sampling when you have reason to focus on where problems are most likely to occur or where resources are best spent.