قارن الطرق

	أخذ العينات بالثلج المتدحرج	العينة القصدية
المجال	منهجية المسح	منهجية المسح
العائلة	Process / pipeline	Process / pipeline
سنة النشأة	1961	Formalized ~1980–1990
صاحب الطريقة	Leo A. Goodman	Michael Quinn Patton (systematic articulation); roots in early qualitative inquiry
النوع	Non-probability sampling technique	Non-probability sampling strategy
المصدر التأسيسي	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
الأسماء البديلة	chain-referral sampling, network sampling, respondent-driven sampling, referral sampling	judgmental sampling, selective sampling, criterion-based sampling, purposeful sampling
ذات صلة	3	4
الملخص	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.	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.