The answer is "2. cluster sampling."
Cluster sampling alludes to a kind of sampling technique . With cluster sampling, the scientist partitions the populace into isolated gatherings, called groups. At that point, a basic random sample of clusters is chosen from the populace. The analyst leads his investigation on information from the inspected clusters.
Contrasted with simple random sampling and stratified sampling, cluster sampling has points of interest and disservices. For instance, given equivalent example sizes, group testing normally gives less accuracy than either simple random sampling or stratified sampling. Then again, if travel costs between clusters are high, cluster sampling might be more practical than alternate strategies.
