The Following Sales Data Are Available for 2003-2008 Calculate the Average Error

Essay

The following sales data are available for 2003-2008:
$$\begin{array} { | c | c | c | } \hline \text { Year } & \text { Sales } & \text { Forecast } \\\hline 2003 & 7 & 9 \\\hline 2004 & 12 & 10 \\\hline 2005 & 14 & 15 \\\hline 2006 & 20 & 22 \\\hline 2007 & 16 & 18 \\\hline 2008 & 25 & 21 \\\hline\end{array}$$
Calculate the average error.