Cluster sampling is a statistical method used to select a sample from a larger population. In this approach, the population is divided into smaller groups, or clusters, which are usually based on geographical areas or other natural groupings. Instead of sampling individuals from the entire population, researchers randomly select entire clusters to study. Once the clusters are chosen, all individuals within those selected clusters may be surveyed, or a random sample from each cluster can be taken. This method is often more practical and cost-effective, especially when the population is large and spread out over a wide area.