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Cluster  (CLUSTER)

A sample whose elements are selected by a chance process is called a probability sample1. If a complete list of sampling units is available this is called a sampling frame3. In simple random sampling4 a proportion of sampling units is selected from the frame at random2. This proportion is called the sampling fraction5. Systematic samples6 are taken from a frame in which the sampling units are consecutively numbered. The sample is drawn by taking the nth, (n + s)th, (n + 2s)th..., etc. unit, where n is not larger than s and is selected at random. In cluster sampling7 population elements are not drawn individually, but in groups which are called clusters8.

  • 2. random — randomness n. — randomize v.