Theoretical sampling refers to the process of choosing new research

Research

Research can be defined as the scientific search for knowledge, or as any systematic investigation, to establish novel facts, solve new or existing problems, prove new ideas, or develop new theories, usually using a scientific method...

 sites or cases to compare with ones that have already been studied. It is one of the tools of qualitative research

Qualitative research

Qualitative research is a method of inquiry employed in many different academic disciplines, traditionally in the social sciences, but also in market research and further contexts. Qualitative researchers aim to gather an in-depth understanding of human behavior and the reasons that govern such...

. The term was coined by Barney Glaser

Barney Glaser

Barney G. Glaser is an American sociologist and one of the founders of the grounded theory methodology.Glaser was born in San Francisco, California, and lives in Mill Valley. He received his BA degree at Stanford in 1952. He pursued academic studies at the University of Paris where he studied...

 and Anselm Strauss

Anselm Strauss

Anselm Leonard Strauss was an American sociologist internationally known as a medical sociologist and as the developer of grounded theory, an innovative method of qualitative analysis widely used in sociology, nursing, education, social work, and...

 in 1967.

The goal of theoretical sampling is not the same as with the probabilistic sampling

Sampling (statistics)

In statistics and survey methodology, sampling is concerned with the selection of a subset of individuals from within a population to estimate characteristics of the whole population....

; the researcher's goal is not the representative capture of all possible variations, but to gain a deeper understanding of analysed cases and facilitate the development of analytic frame

Analytic frame

Analytic frame is a detailed sketch or outline of some social phenomenon, representing initial idea of a scientist analyzing this phenomenon. Charles C. Ragin defines it as one of the four building blocks of social research Analytic frame is a detailed sketch or outline of some social phenomenon,...

 and concept

Concept

The word concept is used in ordinary language as well as in almost all academic disciplines. Particularly in philosophy, psychology and cognitive sciences the term is much used and much discussed. WordNet defines concept: "conception, construct ". However, the meaning of the term concept is much...

s used in their research.

Theoretical sampling can be viewed as a technique of data triangulation: using independent pieces of information to get a better fix on something that is only partially known or understood.