Samples taken in a series of steps with the sampling portions constituting the sample (units or increments) at each step being selected from the larger or greater number of portions of the previous step, or from a primary or @C01212@. The first set of portions (units or increments) taken from the population available for sampling is the @P04841@. The subsequent samples (secondary, tertiary, etc.) are the sets of subsamples, units, items, individuals or increments taken from the preceding step. The units may be different steps of multistage sampling (e.g. pallets, cases, packages).