ABSTRACT
This chapter presents data consisting of observations at successive points of time; such data are said to form a time series. It considers only time series having equal intervals between observations. Time series data can be represented graphically in a line diagram of observations plotted against time as horizontal axis, successive points being joined by straight lines. For such diagrams, the time axis is often of considerable length and rules about the size relationship between horizontal and vertical axes can be relaxed. To isolate the trend, statisticians must use a moving average of such period as to eliminate the seasonal effects. Statisticians are left with seven years’ worth of data containing only seasonal and residual effects. Time series may be decomposable into components representing temporal trend and seasonal variation thus permitting production of de-seasonalized figures.
