Definición Cluster sample

The cluster selection is a special form of random selection. Different to simple random selection, individuals are not selected at random, rather entire groups (or clumps). The stratified random sample should not be confused with the cluster sample. In the stratified random sample, layers are defined and attributes are taken at random from the layers. The cluster analysis is randomly drawn up from all clusters, and all characteristic attributes are examined within any given cluster.

For example: in a university, all students are to be interviewed that have attended seminars in general studies. There are no complete attendance lists, as the students do not have to register for all of the seminars in advance. Therefore, it is impossible to randomly select participants by means of a list. Instead of the 214 seminars offered, 24 are chosen at random. All students within these 24 seminars are then surveyed by distributing questionnaires during the course.