12.1 Objectives

Motivations for Using Time Series

Time-series methods are used to do the following:

• Understand the generative process underlying the observed data
• Fit a model in order to monitor or forecast a process

The basic objective usually is to determine a model that describes the pattern of the time series. Uses for such a model are:

• To describe the important features of the time series pattern.
• To explain how the past affects the future or how two time series can interact.
• To forecast future values of the series.
• To possibly serve as a control standard for a variable that measures the quality of product in some manufacturing situations.