Cluster sampling is defined as a sampling method where multiple clusters of people are created from a population where they are indicative of homogenous characteristics and have an equal chance of being a part of the sample. In this sampling method, a simple random sample is created from the different clusters in the population. This is a probability sampling procedure.
Types of cluster sampling
There are three types as following,
Single stage Cluster: In this process sampling is applied in only one time. For example, An NGO wants to create a sample of girls across five neighboring towns to provide education. Using single-stage sampling, the NGO randomly selects towns (clusters) to form a sample and extend help to the girls deprived of education in those towns.
Two-stage Cluster: In this process, first choose a cluster and then draw sample from the cluster using simple random sampling or other procedure. For example, A business owner wants to explore the performance of his/her plants that are spread across various parts of the U.S. The owner creates clusters of the plants. He/she then selects random samples from these clusters to conduct research.
Multistage Cluster: Few step added to two-stage then it is called multistage cluster sampling. For example, An organization intends to survey to analyze the performance of smartphones across Germany. They can divide the entire country’s population into cities (clusters) and select cities with the highest population and also filter those using mobile devices.
Cluster sampling vs stratified sampling
There are some dissimilarities between cluster and stratified sampling,….(source)
|Cluster sampling||Stratified sampling|
|Elements of a population are randomly selected to be a part of groups (clusters).||The researcher divides the entire population into even segments (strata).|
|Members from randomly selected clusters are a part of this sample.||Researchers consider individual components of the strata randomly to be a part of sampling units.|
|Researchers maintain homogeneity between clusters.||Researchers maintain homogeneity within the strata.|
|Researchers divide the clusters naturally.||The researchers or statisticians primarily decide the strata division.|
|The key objective is to minimize the cost involved and enhance competence.||The key objective is to conduct accurate sampling, along with a properly represented population.|