The following are monthly actual and forecast demand levels for May through December for units of a product manufactured by the D. Bishop Company in? Des? Moines:
Month Actual Demand Forecast Demand
May 108 104
June 82 100
july 112 97
August 115 104
September 108 100
October 106 106
November 130 105
December 120 111
For the? given? forecast, the tracking? signal? =______ MADs