Vertaile menetelmiä

	Painotettu lumipallo-otanta	harkinnanvarainen otanta – kriteereihin perustuva tapausten valinta
Tieteenala	Kyselytutkimuksen metodologia	Kyselytutkimuksen metodologia
Menetelmäperhe	Process / pipeline	Process / pipeline
Syntyvuosi	1997	Formalized ~1980–1990
Kehittäjä	Douglas D. Heckathorn (formal probability-weighted variant)	Michael Quinn Patton (systematic articulation); roots in early qualitative inquiry
Tyyppi	Probability-adjusted chain-referral sampling	Non-probability sampling strategy
Alkuperäislähde	Heckathorn, D. D. (1997). Respondent-driven sampling: A new approach to the study of hidden populations. Social Problems, 44(2), 174–199.	Patton, M. Q. (1990). Qualitative Evaluation and Research Methods (2nd ed.). Sage. ISBN: 978-0803937796
Rinnakkaisnimet	weight-adjusted chain-referral sampling, probability-weighted snowball sampling, WSS, weighted referral sampling	judgmental sampling, selective sampling, criterion-based sampling, purposeful sampling
Liittyvät	5	4
Tiivistelmä	Weighted snowball sampling is a chain-referral technique in which participants recruit peers from a hidden or hard-to-reach population, and differential inclusion probabilities are estimated and corrected through statistical weights. Unlike basic snowball sampling, the weighting step allows approximately unbiased population estimates, bridging the gap between convenience-driven recruitment and probability-based inference.	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.