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 (every 10th unit) being used to select the sample.
2. Review the definitions of sampling methods: Simple random sampling involves selecting units completely at random. Stratified sampling involves dividing the population into subgroups (strata) and sampling from each subgroup. 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 10th unit, this aligns with 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 but follows a fixed interval. Stratified sampling is not used because there is no division into subgroups. Cluster sampling is not used because entire clusters are not being sampled.
5. Conclude that the sampling method used is systematic sampling, as it matches the definition of selecting every nth unit from the population.