We will now consider not the probability of observing particular events but rather the events themselves and try to find a particularly simple way of classifying them. We can, for instance, associate the event “heads” with the number 0 and the event “tails” with the number 1. Generally we can classify the events of the decomposition (2.3.3) by associating each event A i ; with the real number i. In this way each event can be characterized by one of the possible values of a random variable. Random variables can be discrete or continuous. We denote them by symbols like x, y,....