To survey employees, a researcher obtains a list of extensions and selects every 510th person. What sampling technique is this?

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

Answer: (C)

Systematic sampling uses a fixed interval from an ordered list to select participants. Here, choosing every 510th person from the list of extensions is exactly applying that constant interval. This differs from simple random sampling, where selections are made purely by chance without a set pattern. It’s also not stratified sampling, which means sampling within predefined subgroups, nor cluster sampling, which involves sampling whole groups. The approach is efficient and tends to spread selections across the list, but it can introduce bias if there’s a hidden pattern in the list that aligns with the interval.