手法を比較

	逸脱事例サンプリング	スノーボールサンプリング（またはチェーン紹介サンプリング）
分野	調査方法論	調査方法論
系統	Process / pipeline	Process / pipeline
提唱年	1990	1961
提唱者	Michael Quinn Patton	Leo A. Goodman
種類	Purposive qualitative sampling strategy	Non-probability sampling technique
原典	Patton, M. Q. (2002). Qualitative Research and Evaluation Methods (3rd ed.). Sage Publications. ISBN: 978-0761919711	Goodman, L. A. (1961). Snowball sampling. Annals of Mathematical Statistics, 32(1), 148–170.
別名	extreme case sampling, outlier sampling, negative case sampling, deviant-case selection	chain-referral sampling, network sampling, respondent-driven sampling, referral sampling
関連	5	3
概要	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.	Snowball sampling is a non-probability recruitment technique in which initial participants (seeds) refer the researcher to others who meet the study criteria, and those referrals in turn refer further participants. The sample grows incrementally — like a rolling snowball — until the required size or theoretical saturation is reached. It is the method of choice when a target population has no accessible sampling frame, such as undocumented migrants, illicit drug users, survivors of stigmatised experiences, or members of closed professional networks.