A Forecasting Method Has Produced the Following Over the Past

Multiple Choice

A forecasting method has produced the following over the past five months. What is the mean absolute deviation?
$\begin{array}{|c|c|c|c|}\hline \text { Actual } & \text { Forecast } & \text { Error } & \mid \text { Error } \mid \\\hline 10 & 11 & -1 & 1 \\\hline 8 & 10 & -2 & 2 \\\hline 10 & 8 & 2 & 2 \\\hline 6 & 6 & 0 & 0 \\\hline 9 & 8 & 1 & 1 \\\hline\end{array}$

A) -0.2
B) -1.0
C) 0.0
D) 1.2
E) 8.6