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	Kvotsampling – Icke-sannolikhetsbaserat kontrollerat urval	Snöbollsurval
Ämnesområde	Surveymetodik	Surveymetodik
Familj	Process / pipeline	Process / pipeline
Ursprungsår	1930s	1961
Upphovsperson	Developed in market research and opinion polling, notably applied by George Gallup in the 1930s	Leo A. Goodman
Typ	Non-probability sampling design	Non-probability sampling technique
Ursprungskälla	Moser, C. A., & Kalton, G. (1972). Survey Methods in Social Investigation (2nd ed.). Heinemann. ISBN: 978-0435827496	Goodman, L. A. (1961). Snowball sampling. Annals of Mathematical Statistics, 32(1), 148–170.
Alias	quota-controlled sampling, quota selection, non-probability quota sampling	chain-referral sampling, network sampling, respondent-driven sampling, referral sampling
Närliggande	5	3
Sammanfattning	Quota sampling is a non-probability technique in which the researcher pre-specifies how many units to recruit from each subgroup (quota cell) defined by one or more control variables such as age, gender, or occupation. Interviewers or data collectors then use their own judgment to find and enroll participants until each cell is filled. The method guarantees the sample mirrors the population on the control variables but does not provide the randomness needed for classical statistical inference.	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.