So sánh phương pháp

	Lấy mẫu trường hợp lệch 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	1980s–1990s (purposive/deviant case sampling literature)	Formalized ~1980–1990
Người khởi xướng	Michael Quinn Patton; Yvonna Lincoln & Egon Guba	Michael Quinn Patton (systematic articulation); roots in early qualitative inquiry
Loại	Purposive qualitative sampling strategy	Non-probability sampling strategy
Công trình gốc	Patton, M. Q. (2002). Qualitative Research and Evaluation Methods (3rd ed.). Sage Publications. ISBN: 978-0761919711	Patton, M. Q. (1990). Qualitative Evaluation and Research Methods (2nd ed.). Sage. ISBN: 978-0803937796
Tên gọi khác	field deviant case sampling, outlier case sampling in field research, extreme case sampling in fieldwork, in-situ deviant case sampling	judgmental sampling, selective sampling, criterion-based sampling, purposeful sampling
Liên quan	5	4
Tóm tắt	Field-based deviant case sampling is a purposive strategy that deliberately selects cases deviating markedly from an established pattern or norm, with data collected through direct fieldwork — observation, in-situ interviews, and ethnographic engagement — in the participants' natural settings. By studying outliers on-site, researchers gain contextually grounded insight into why and how certain cases diverge from the typical pattern.	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.