Which sampling technique involves selecting every nth unit from a list?

• A. Convenience Sampling
• B. Snowball Sampling
• C. Stratified Sampling
• D. Systematic Sampling

Answer: (D)

Systematic sampling is the method that selects every nth unit from a list. You decide how many units you want to sample and then pick a random starting point within the first interval, continuing down the list by a fixed gap. This approach spreads the sample evenly across the population and is quick and easy to implement because you just follow a regular pattern rather than choosing units individually. The interval is typically determined by dividing the population size by the desired sample size. A potential pitfall is if the list has a repeating pattern that matches the interval, which can bias the results. This differs from convenience sampling (choosing readily available individuals), snowball sampling (referrals from initial subjects), and stratified sampling (dividing into subgroups and sampling within each).