A stochastic process is a collection or ensemble of random variables indexed by a variable t,
usually representing time. It means that one has a system for which there are observations at
certain times, and that the outcome, that is, the observed value at each time is a random
variable. Since stochastic processes provide a method of quantitative study through the
mathematical model, it plays an important role in the modern discipline or operations research.
The waiting-line analysis or queuing problem of operations research is the most important part
in which the theory of stochastic processes applies most often.