So sánh phương pháp

	Phương pháp chọn mẫu Snowball dựa trên thực địa	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	1961 (foundational); field variant developed through 1970s–1980s ethnographic and hidden population research	Formalized ~1980–1990
Người khởi xướng	Leo A. Goodman (snowball sampling); field adaptation through ethnographic and social network research traditions	Michael Quinn Patton (systematic articulation); roots in early qualitative inquiry
Loại	Non-probability sampling technique	Non-probability sampling strategy
Công trình gốc	Goodman, L. A. (1961). Snowball sampling. Annals of Mathematical Statistics, 32(1), 148–170.	Patton, M. Q. (1990). Qualitative Evaluation and Research Methods (2nd ed.). Sage. ISBN: 978-0803937796
Tên gọi khác	in-person snowball sampling, fieldwork chain-referral sampling, field snowball sampling, face-to-face referral sampling	judgmental sampling, selective sampling, criterion-based sampling, purposeful sampling
Liên quan	3	4
Tóm tắt	Field-based snowball sampling is a non-probability chain-referral technique in which an initial set of in-person contacts (seeds) recruit further participants from within their real-world social networks, expanding the sample iteratively through face-to-face interaction in naturalistic field settings. It is the default snowball approach in ethnographic and community fieldwork, and is particularly valuable when the target population is hidden, hard-to-reach, or lacks a sampling frame.	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.