Compară metode

	Eșantionare Sistematică	Eșantionarea pe grupe (Cluster Sampling)
Domeniu	Metodologia anchetelor	Metodologia anchetelor
Familie	Process / pipeline	Process / pipeline
Anul apariției	Mid-20th century (Cochran 1953; Kish 1965)	Early-to-mid 20th century; canonical treatment 1953/1977
Autorul original	William G. Cochran; formalized in survey sampling theory	Formalized by William G. Cochran; roots in early 20th-century U.S. Census Bureau survey practice
Tip	Probability sampling design	Probability sampling design
Sursa seminală	Cochran, W. G. (1977). Sampling Techniques (3rd ed.). John Wiley & Sons. ISBN: 978-0471162407	Cochran, W. G. (1977). Sampling Techniques (3rd ed.). Wiley. ISBN: 978-0471162407
Denumiri alternative	interval sampling, systematic random sampling, equal-interval sampling, fixed-interval sampling	cluster random sampling, area sampling, one-stage cluster sampling
Înrudite	5	5
Rezumat	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.	Cluster sampling is a probability sampling technique in which the population is divided into naturally occurring groups (clusters), a random sample of clusters is selected, and all — or a random subset of — members within each selected cluster are studied. It is especially practical when a complete population list is unavailable or when units are geographically dispersed, making individual random selection prohibitively expensive. One-stage cluster sampling surveys every member of selected clusters; two-stage designs add a second random draw within clusters.