Two-stage sample

A simple case of a multi-stage sample. In this case the population to be sampled is first classified into primary units, each of which consists of a collection of the basic sampling unit, the secondary unit. A sample of these primary units is taken, constituting the first stage, and these are then subsampled with respect to their secondary units: this constitutes the second stage. OECD Source: A Dictionary of Statistical Terms, 5th edition, prepared for the International Statistical Institute by F.H.C. Marriott. Published for the International Statistical Institute by Longman Scientific and Technical.