Cluster sampling is also known as the probability sampling approach where you can divide a population into groups, such as districts or schools, and then select a representative sample from among these groups at random. A modest representation of the population as a whole should be present in each cluster.
A probability sampling strategy called systematic sampling involves picking people from the population at regular intervals, such as every 15th person on a population list. The population can be organized randomly to mimic the benefits of simple random sampling.