When it is difficult to receive information beforehand about how many and which participants are present in the population, the cluster sampling method is used frequently. Here, the researcher does not draw individuals from the population, but clusters of possible participants. These clusters are often based on naturally occurring clusters, such as regions within a country. Often, multistage sampling is used with cluster sampling. With multistage sampling, large clusters are determined first. Next, smaller clusters within these large clusters are determined. This continues until a sample emerges with randomly chosen participants from each cluster.