Which sampling method uses a fixed interval to select subjects from an ordered list after a random start?

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

Answer: (B)

Systematic sampling is being tested here. You take an ordered list, pick a starting point at random, and then select every fixed interval item, or every kth item. This regular pattern means you’re spread across the list without needing to randomize each selection, and the random start helps reduce bias from the list’s order. It’s efficient and easy to implement, especially when you already have a complete list. If the list’s order is related to the variable you’re studying, bias can still occur. This approach differs from a purely random selection, which has no fixed interval; from stratified sampling, which divides the population into subgroups and samples from each; and from cluster sampling, which involves selecting entire groups rather than following a fixed interval across an ordered list.