Answer:
The value of the tracking signal as of the end of December is 8.
Explanation:
month actual forecast forecast RSFE absolute MAD Tracking signal
sales sales error error
May 105 102 3 3 3 3 1
june 78 104 -26 -23 -26 -11.5 2
july 108 101 7 -16 7 -5.33333 3
august 112 104 8 -8 8 -2 4
sep 108 104 4 -4 4 -0.8 5
oct 110 104 6 2 6 -0.6667 -3
nov 125 105 20 22 20 3.142857143 7
dec 125 109 16 38 16 4.75 8
