Stratified sample

"A probability sample in which people are selected because they come from distinct sub-groups within the society. This approach may be used by ethnographers if the information that is being sought is not specialized knowledge such as the esoteric activities of a secret organization with restricted membership. (this sort of sample is often used by ux designers when trying to determine the different possible users and user scenarios of a site in hHCI research. they are also known as "personas" and are often invented". http://anthro.palomar.edu/tutorials/cglossary.htm