A new method and an algorithm of ensuring the uniformity of normalized samples of technical and economic parameters of power units of thermal power plants are presented. Uniformity and normalization are obligatory conditions at estimation of integrated parameters characterizing the efficiency of power units. The method is based on the fiducial approach. Boundary values of fiducial interval are traditionally calculated based on the statistical function of distribution and a set significance value, i.e. are calculated, in fact, "mechanically". As the "mechanical" approach is appropriate for homogeneous statistical data, whereas technical and economic parameters are multivariate data, application of this approach to the statistical function of fiducial distribution is associated with a high risk of an erroneous decision. The set of possible realizations of actual values of technical and economic parameters includes realizations caused by "gross" mistakes at data input in automated systems or at manual performance of individual calculations. Quite often, unconventional realizations are observed, e. g., in case of low-load operation for 10 days of a month. These data form boundary intervals that the authors refer to as “boundins” (or prigrins in Russian). Automated search and removal of boundins provides reliability of comparison and ranking of integrated parameters. It is shown that rate of variation of boundins is considerably below the rate of variation of typical realizations of technical and economic parameters. This fact was the basis for recognition of boundins.