This is intended to specify suitable values of statistics which allow an assessment of the detection capabilities in spectrometric nuclear radiation measurements and of the physical effect quantified by a measurand (for example a net of a spectrometric line in an alpha- or gamma-spectrum) which is determined by evaluation of a multichannel spectrum by unfolding methods. By use of one or multiple lines of a radionuclide activities or an activity concentration of this radionuclide can be evaluated with the help of a suitable model.