ABSTRACT
In this chapter we shall discuss random fluctuations of life times associated with people, animals and machines. As we adopt a probabilistic point of view, it is appropriate to begin with a precise formulation of our intuitive notion of probability, and establish rules for calculations. Next, we shall define what we mean by life time, and state how it can be described in a convincing way. Then, we shall engage in the study of numerous examples of diverse nature, involving one life time, combinations of life times, and highly interesting associated features like cost functions, averages, distribution functions, densities and other normal and abnormal situations. Proceeding step-by-step, we shall develop our probabilistic tools as the need arises. It is the rewarding applications which will gratify our efforts in acquiring these tools. So let us hope for easy life and good times!
