So sánh phương pháp

	Chọn mẫu hạn ngạch	Lấy mẫu có hệ thống
Lĩnh vực	Phương pháp luận khảo sát	Phương pháp luận khảo sát
Họ	Process / pipeline	Process / pipeline
Năm ra đời	1930s	Mid-20th century (Cochran 1953; Kish 1965)
Người khởi xướng	Developed in market research and opinion polling, notably applied by George Gallup in the 1930s	William G. Cochran; formalized in survey sampling theory
Loại	Non-probability sampling design	Probability sampling design
Công trình gốc	Moser, C. A., & Kalton, G. (1972). Survey Methods in Social Investigation (2nd ed.). Heinemann. ISBN: 978-0435827496	Cochran, W. G. (1977). Sampling Techniques (3rd ed.). John Wiley & Sons. ISBN: 978-0471162407
Tên gọi khác	quota-controlled sampling, quota selection, non-probability quota sampling	interval sampling, systematic random sampling, equal-interval sampling, fixed-interval sampling
Liên quan	5	5
Tóm tắt	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.	Systematic sampling is a probability sampling technique in which every k-th element is selected from an ordered list of the population after a random starting point. With population size N and desired sample size n, the sampling interval k = N/n is computed and one unit is chosen at random from the first interval; all subsequent units are selected by adding k repeatedly. The method is operationally simple, yields a spread-out sample, and often achieves lower variance than simple random sampling when the list has no harmful periodicity.