In this article the problem of statistically reliable sample size evaluation is considered. The two step procedure proposed by C. Stain allows to determine the sample size. The C. Stain's procedure was used for creating the program `The evaluation of data representation'. The program is a part of the program shell of `Servis-Base' data-base software, developed by the authors. The program was used for the evaluation of the sufficient quantity of measurings in experiments for the determination of the proteinase B.intermedius productivity
