ABSTRACT
For deterministic systems, information about the state of the system at time determines with certainty its state at any later time. For stochastic systems, on the other hand, no such certainty can be achieved, viz. the knowledge of the state of the system at a specified time, enables us to predict only the probability that the system be in any of several possible states in the future. This chapter describes the basic logical steps that lead to such stochastic models. It also describes several stochastic models for various growth and decay processes and compare to some extent their predictions with the corresponding deterministic ones. The chapter explores a general mathematical model constructed by Kermack and McKendrick for the spread of epidemics, rumors, and so on within a given population of M + 1 individuals.
