The selection of soil parameters suitable to the geotechnical design calculations is regarded widely as one of the most important and simultaneously difficult engineering task, which according to the EC 7 should be undertaken into distinct three steps. The second of these steps requires careful and caution estimation with application of the statistical methods even by using a Bayesian approach as shown in this paper. It presents the process of selecting a characteristic strength and deformation parameters from CPT and DMT investigation for boulder clays found in SGGW Campus (Warsaw). This layer was chosen for foundations of design academic buildings. In the selection of the characteristic parameters with application of the numerical program BAYANAL the spatial distribution was taken into account. Particular attention was focused to the affect resulting from in situ test locations at different distances from the design facilities. Finally, the remark conclusions were presented including an approach with weights proposed to determination of the conclusive characteristic values.