The object of this study is the assessment of total uncertainty during calibration in terms of assessing the component due to the competence of the personnel. The problems addressed here related to the lack of regulatorily-defined decision criteria regarding the materiality of the impact of the study component; improvement of existing statistics that would minimize errors of the first and second kinds to make a decision on the impact of personnel competence on uncertainty during calibration. A brief interpretation of the results obtained regarding errors of the first and second kinds and insufficient power of En, the statistics, which are most often used by calibration laboratories, alternative statistics are explained by violation of the conditions of their use. The proposed method based on the modified En-statistics shows the power of more than 95 % and the absence of parcels of the first and second kinds. This is due to the developed modification, which makes it possible to take into consideration the maximum permissible uncertainty. The peculiarity is the flexibility of the formula since the maximum permissible uncertainty is chosen according to metrological rules for the selection of standards. It differs for various measuring instruments; a specialist can be allowed to calibrate a less accurate measuring equipment tools and is not allowed to have high-precision ones. The scope of use of the obtained results can be certified calibration laboratories. This procedure will make it possible to obtain reliable data to devise internal methods for assessing uncertainty during calibration. The conditions for the practical use of the proposed method of assessing the impact of personnel based on the modified En-statistics in calibration laboratories are the presence of calibration methods that largely depend on the competence of the personnel, such as measurement of linear and mechanical quantities