Although methodically even simpler, this alternative lacks one central feature of the method described in Section 2.2: Geological classes are being investigated individually one by one and therefore independently. The method proposed in this paper, on the other hand, investigates assemblages involving all classes simultaneously. Its statistical results therefore refer to the assemblages, i.e. groupings of classes into a sub-group of RPG and one of non-RPG, and not to individual classes. The latter are independent on how classes are assembled into one sub-set “RPG” and the other, “non-RPG”.