REPRESENTATIVE SAMPLING OF STREET DRUG EXHIBITS

The value of a scientific analysis and the significance of the results are influenced by the degree to which the sample analyzed reflects th e composition of the material or population under study. An appropriat e methodology will result in representative sampling. Formulae for rep resentative sampling protocols were evaluated, and an optimal formula to be used in a sampling plan for ''street'' drug exhibits with a larg e number of units was selected. The selected formula was applied to ch oose a number of sample units for routine chemical analysis of control led substances, with the analytical result considered to be representa tive of the entire lot of powdered drug units in the exhibit. The resu lts obtained during the research demonstrate that adoption of the form ula n = 20 + 10%(N - 20) [where n = sample size, N = total population (N greater-than-or-equal-to 20)] can be used for selection of an appro priate representative sample from powdered street-drug exhibits. This sampling procedure results in forensic analyses of controlled substanc es which are supportable to a reasonable scientific certainty, and whi ch are obtained in an efficient manner.