In the cluster sample, the population is divided into subpopulations, which are generally smaller than stratified samples. The survey then takes place only in randomly selected lumps.
Belonging to a lump does not result from a systematically selected feature, but from the existing possibilities of dividing the sampling units. These are often regionally bound lumps. Within the selected lumps random samples are drawn for the survey.
infas uses clumped samples by default in residents' registration offices where communities or neighborhoods define the clumps