So sánh phương pháp

	Lấy mẫu ngẫu nhiên đơn giản	Chọn mẫu có chủ đích
Lĩnh vực	Phương pháp luận khảo sát	Phương pháp luận khảo sát
Họ	Process / pipeline	Process / pipeline
Năm ra đời	Early 20th century; systematized by Cochran 1953/1977	Formalized ~1980–1990
Người khởi xướng	William Gosset, Jerzy Neyman, and formalized by William Cochran	Michael Quinn Patton (systematic articulation); roots in early qualitative inquiry
Loại	Probability sampling design	Non-probability sampling strategy
Công trình gốc	Cochran, W. G. (1977). Sampling Techniques (3rd ed.). John Wiley & Sons. ISBN: 978-0471162407	Patton, M. Q. (1990). Qualitative Evaluation and Research Methods (2nd ed.). Sage. ISBN: 978-0803937796
Tên gọi khác	SRS, unrestricted random sampling, equal-probability sampling, EPSEM	judgmental sampling, selective sampling, criterion-based sampling, purposeful sampling
Liên quan	6	4
Tóm tắt	Simple random sampling (SRS) is the foundational probability sampling method in which every unit in the population has an equal and independent chance of being selected. Because selection is governed purely by chance, SRS eliminates systematic bias, supports unbiased estimation of population parameters, and provides the statistical baseline against which all more complex probability designs are evaluated.	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.