Probability and Random Variables
During the course of history many people devoted much thought to the subject of probability (Schneider 1986). For a long time people sought in vain to define precisely what is meant by probability. In 1933 the Russian mathematician A. N. Kolmogorov formulated a complete system of axioms for a mathematical definition of probability. Today this system is the basis of probability theory and mathematical statistics. We speak of the probability of events. This means that a number is assigned to each event and this number should represent the probability of this event. Let us consider throwing a die as an example. In this case each possible event is an outcome showing a certain number of points, and one would assign the number 1/6 to each event. This expresses the fact that each event is equally likely, as expected for a fair die, and that the sum of the probabilities is normalized to 1. The Kolmogorov system of axioms now specifies the structure of the set of events and formulates the rules for the assignment of real numbers (probabilities) to these events.