So sánh phương pháp

	Lấy mẫu Quả cầu tuyết có trọng số	Chọn mẫu có chủ đích
Lĩnh vực	Phương pháp luận khảo sát	Phương pháp luận khảo sát
Họ	Process / pipeline	Process / pipeline
Năm ra đời	1997	Formalized ~1980–1990
Người khởi xướng	Douglas D. Heckathorn (formal probability-weighted variant)	Michael Quinn Patton (systematic articulation); roots in early qualitative inquiry
Loại	Probability-adjusted chain-referral sampling	Non-probability sampling strategy
Công trình gốc	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
Tên gọi khác	weight-adjusted chain-referral sampling, probability-weighted snowball sampling, WSS, weighted referral sampling	judgmental sampling, selective sampling, criterion-based sampling, purposeful sampling
Liên quan	5	4
Tóm tắt	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.