What is the process of selecting every nth item in a population called?

The process of selecting every nth item in a population is known as systematic sampling. This method involves arranging the population in some logical order (such as alphabetical or chronological) and then selecting members at regular intervals. For example, if a researcher decides to select every 10th member from a list of participants, they would systematically gather data that can help ensure a level of representation across the population.

Systematic sampling is often used because it is straightforward and can be less time-consuming than other methods of sampling, such as random sampling, which requires a more complex process to ensure each member has an equal chance of being selected. The regularity of the selection can help to avoid clustering of items and can lead to more evenly distributed samples. This method is particularly useful in situations where a complete list of the population is available.