As you will have noticed in ► Chaps. 17 – 20 , in statistics we are not always dealing with intermediate results or parameters that can be calculated in concrete terms. Now and then—because the calculation would be too costly or is simply impossible due to the large number of factors to be taken into account—we have no choice but to make reasonable estimates with regard to certain parameters. This applies in particular if these are to represent the bases of estimation functions for the determination of unknown parameters of measured value distributions.