This term is used in two different senses; one related to multi-stage sampling and the other to multi-phase sampling. In multi-stage sampling the process of selecting sample units, say, at the second stage from any selected first stage unit is called subsampling of the first stage unit. In multi-phase sampling that part, say, of the first-phase sample which is taken up for the second phase inquiry is said to constitute a subsample of the first phase sample, and the process of selection at the second phase may be called subsampling.