Vertaile menetelmiä

	harkinnanvarainen otanta – kriteereihin perustuva tapausten valinta	Osallistujapohjainen otanta
Tieteenala	Kyselytutkimuksen metodologia	Kyselytutkimuksen metodologia
Menetelmäperhe	Process / pipeline	Process / pipeline
Syntyvuosi	Formalized ~1980–1990	1997
Kehittäjä	Michael Quinn Patton (systematic articulation); roots in early qualitative inquiry	Douglas Heckathorn
Tyyppi	Non-probability sampling strategy	Probabilistic chain-referral sampling design
Alkuperäislähde	Patton, M. Q. (1990). Qualitative Evaluation and Research Methods (2nd ed.). Sage. ISBN: 978-0803937796	Heckathorn, D. D. (1997). Respondent-driven sampling: A new approach to the study of hidden populations. Social Problems, 44(2), 174–199.
Rinnakkaisnimet	judgmental sampling, selective sampling, criterion-based sampling, purposeful sampling	Chain-Referral Sampling, Peer-Referral Sampling, Network-Based Sampling, Katılımcı Güdümlü Örnekleme
Liittyvät	4	3
Tiivistelmä	Purposive sampling is a non-probability strategy in which the researcher deliberately selects participants, documents, or cases that are information-rich with respect to the research question. Rather than drawing units at random, the researcher applies explicit criteria aligned with the study's purpose, maximising the depth and relevance of the data collected. It is the default sampling logic in most qualitative research designs and is also used in mixed-methods and applied evaluative work.	Respondent-Driven Sampling (RDS) is a probabilistic chain-referral method designed to reach hidden or hard-to-reach populations that lack a sampling frame. Introduced by sociologist Douglas Heckathorn in 1997, RDS combines snowball recruitment with mathematical weighting based on participants' personal network sizes, allowing researchers to generate population-level estimates even when no complete membership list exists.