مقایسهٔ روش‌ها

	نمونه‌گیری هدفمند	نمونه‌گیری موارد انحرافی
حوزه	روش‌شناسی پیمایش	روش‌شناسی پیمایش
خانواده	Process / pipeline	Process / pipeline
سال پیدایش	Formalized ~1980–1990	1990
پدیدآور	Michael Quinn Patton (systematic articulation); roots in early qualitative inquiry	Michael Quinn Patton
نوع	Non-probability sampling strategy	Purposive qualitative sampling strategy
منبع بنیادین	Patton, M. Q. (1990). Qualitative Evaluation and Research Methods (2nd ed.). Sage. ISBN: 978-0803937796	Patton, M. Q. (2002). Qualitative Research and Evaluation Methods (3rd ed.). Sage Publications. ISBN: 978-0761919711
نام‌های دیگر	judgmental sampling, selective sampling, criterion-based sampling, purposeful sampling	extreme case sampling, outlier sampling, negative case sampling, deviant-case selection
مرتبط	4	5
خلاصه	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.	Deviant case sampling is a purposive qualitative sampling strategy in which the researcher intentionally selects cases that are unusual, exceptional, or markedly different from the norm — outliers, extreme successes, or conspicuous failures. The goal is not statistical representation but deep learning from cases that illuminate the boundaries of a phenomenon, challenge prevailing assumptions, or reveal processes that typical cases obscure.