Sample size for inspection intended to manage risk within mixed consignments

Abstract

The identification of a lot, and the size of the random sample taken for plant products, is justified by appeal to International Standards for Phytosanitary Measures No. 31, "Methodologies for Sampling of Consignments". ISPM 31 notes that "A lot to be sampled should be a number of units of a single commodity identifiable by its homogeneity [...]" and "Treating multiple commodities as a single lot for convenience may mean that statistical inferences cannot be drawn from the results of the sampling." However, consignments are frequently heterogeneous, either because the same commodities have multiple sources or because there are several different commodities. The ISPM 31 prescription creates a..