A statistical investigation has been carried out on the accu. racy and precision of the analytical method of automatic determination of enzymes in detergent powders. The statistical design may be applied to any investigation in w h i h the optimizing of the number of trials is required as a function of the wanted precision and supportable costs. A table, that reports the half-range, as a percentage, of the 950/0 confidence interval on the base of the concentration values of the enzyme and carried out samplings, has been obtained. By means of this table and with suitable interpolations, every operator may fix beforehand the number of samples to examine, if a certain precision must be obtained, or conversely the range of the confidence interval got on the base of the number of samplings. The experimental data have been elaborated by a desk computer, introducing in the machine the resulting absorbance values.