A time series is a sequence of observations of a random variable. Hence, it is a stochastic
process. Examples include the monthly demand for a product, the annual freshman
enrollment in a department of a university, and the daily volume of flows in a river.
Forecasting time series data is important component of operations research because these
data often provide the foundation for decision models. An inventory model requires
estimates of future demands, a course scheduling and staffing model for a university
requires estimates of future student inflow, and a model for providing warnings to the
population in a river basin requires estimates of river flows for the immediate future.