Theoretical sampling is mainly used in which type of research?

Theoretical sampling is primarily utilized in qualitative research because it is a strategy that aims to develop and refine theories based on the data collected during the study. In qualitative research, the goal is often to gain an in-depth understanding of social phenomena, and theoretical sampling allows researchers to select cases or participants that are most likely to produce rich and relevant data for the specific theory being tested or developed.

This method contrasts with other sampling techniques such as random sampling, which is more commonly associated with quantitative research. In quantitative research, the focus is on obtaining a representative sample to generalize findings, rather than on theory development. Similarly, while mixed-methods research encompasses both qualitative and quantitative components, it typically does not rely solely on theoretical sampling as a foundational approach. Field experiments, on the other hand, generally employ random sampling or specific selection methods aligned with experimental design rather than theoretical sampling strategies.

Therefore, the focus of theoretical sampling aligns well with qualitative research's objectives and methodology, making it the most appropriate choice.