In games of chance, in the problems of insurance, and in the molecular processes we find events repeating themselves again and again. They are mass p… - Richard von Mises

Apart from this older generation, there is scarcely a modern mathematician who still adheres without reservation to the classical theory of probability. The majority have more or less accepted the frequency definition.

Insurance companies nowadays apply the principle of so-called 'selection by insurance'; this means that they take into consideration the fact that persons who enter early into insurance contracts are on the average of a different type and have a different distribution of death ages from persons from persons admitted to the insurance at a more advanced age.

If the concept of probability and the formulae of the theory of probability are used without a clear understanding of the collectives involved, one may arrive at entirely misleading results.