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	Campionamento Purposivo Multi-livello	Campionamento Stratificato
Campo	Metodologia delle indagini	Metodologia delle indagini
Famiglia	Process / pipeline	Process / pipeline
Anno di origine	1980s–1990s	1977
Ideatore	Derived from Patton's purposive sampling framework; formalized in multi-site qualitative and mixed-methods research	William G. Cochran
Tipo	Non-probability sampling strategy	Probability-based survey sampling design
Fonte seminale	Patton, M. Q. (2002). Qualitative Research and Evaluation Methods (3rd ed.). Sage. ISBN: 978-0761919711	Cochran, W. G. (1977). Sampling Techniques (3rd ed.). Wiley. ISBN: 978-0-471-16240-7
Alias	hierarchical purposive sampling, nested purposive sampling, multi-tier purposive sampling, multi-site purposive sampling	Proportional Stratified Sampling, Optimal Allocation Sampling, Stratum-Based Sampling, Tabakalı Örnekleme
Correlati	5	2
Sintesi	Multi-level purposive sampling applies purposive selection criteria at two or more nested levels of a research hierarchy — for instance, first selecting sites or organizations, then selecting participants within each site. This layered approach allows researchers to align the theoretical logic of purposive sampling with the real-world structure of complex, hierarchical populations, making it especially valuable in multi-site qualitative studies and mixed-methods research.	Stratified sampling is a probability sampling design in which the target population is partitioned into non-overlapping, exhaustive subgroups called strata, and independent probability samples are drawn within each stratum. Formalized by William G. Cochran in Sampling Techniques (1977), the method exploits known population structure to reduce variance and guarantee representativeness of all major subgroups, making it a cornerstone of large-scale survey research and official statistics.