ABSTRACT
In multi-stage sampling, the sample is selected in stages, the sampling units in each stage being sub-sampled from the (larger) units chosen at the previous stage, with appropriate methods of selection of the units - simple random sample (with or without replacement), systematic, probability proportional to size etc. - being adopted at each stage. In other words, the universe is divided into a number of first-stage (or primary sampling) units, which are sampled; then the selected first-stage units are sub-divided into a number of smaller second-stage (or secondary sampling) units, which are again sampled: the process is continued until the ultimate sampling units are reached.
