A quality control manager wants to see how many defective products come off the line on average per day. They select every tenth unit produced on the line and inspect it to see if it is defective. What type of sampling method is this?

• A. Simple random sampling
• B. Stratified sampling
• C. Cluster sampling
• D. Systematic sampling

Answer: (D)

Verified step by step guidance

1. Understand the problem: The quality control manager is selecting every tenth unit produced on the line for inspection. This means there is a fixed, systematic interval between the selected units.
2. Review the definitions of sampling methods: Simple random sampling involves selecting units completely at random. Stratified sampling divides the population into subgroups (strata) and samples from each. Cluster sampling involves dividing the population into clusters and sampling entire clusters. Systematic sampling involves selecting every nth unit from a population.
3. Identify the key characteristic of the sampling method used: Since the manager is selecting every tenth unit, this matches the definition of systematic sampling, where a fixed interval is used to select samples.
4. Eliminate other options: Simple random sampling is not used because the selection is not random. Stratified sampling is not used because there are no subgroups being sampled. Cluster sampling is not used because entire clusters are not being sampled.
5. Conclude that the sampling method used in this scenario is systematic sampling, as it involves selecting every tenth unit in a systematic manner.