All of the following holds true about cluster sampling, except:
Is a Rapid and simple method
Samples are similar to those in Simple Random Sampling
It is a type of probability sample
The sample size may vary according to study design
Cluster sampling is entirely different from Random sampling. The following are differences between random sampling and cluster sampling. Ref: Park's Texbook of Preventive and Social Medicine 19th Edition; Pages 702; High Yield Biostatistics by Anthony N. Glaser 2nd Edition, Pages 2 -3; Methods in Biostatistics By Mahajan6th Edition, Pages 96 - 100; Sampling of Populations: Methods and Applications By Paul S. Levy, Stanley Lemeshow 4th Edition; Pages 269 - 272; 223 - 229.