1) Compute forecast 2) Compute MAD 3) Compute Tracking Signal Homework: GP #2 Ch
ID: 391332 • Letter: 1
Question
1) Compute forecast
2) Compute MAD
3) Compute Tracking Signal
Homework: GP #2 Ch. 4 Forecasting Score: 0 of 10 pts Problem 4.59 4 of 4 (3 complete) HW Score: 75%, 30 of 40 pts Question Help Sales of tablet computers at Ted Glickman's electronics store in Washington, D.C., over the past 10 weeks are shown in the table below: Week 2 3 6 9 10 Demand 21 21 2837 26 2937 22 24 28 a) The forecast for weeks 2 through 10 using exponential smoothing with = 0.55 and a week 1 initial forecast of 21.0 are (round your responses to two decimal places) Week 2 3 6 9 10 Demand 21 2128 37 26 29 37 22 24 28 Forecast 21.0Explanation / Answer
The formula for forecast basis exponential smoothing as follows :
Ft = alpha x At-1 + ( 1 – alpha) x Ft-1 = 0.55 xAt-1 + 0.45x Ft-1
Ft, ft-1 = forecasts for period t and t-1 respectively
At-1 = Actual demand for period t-1
Alpha = smoothing constant = 0.55
Basis above, forecast values for all weeks are presented in the below table.
Also to be noted :
Forecast error for period t = At – Dt
RSFE t = Running sum of forecast error for period t = Sum of all forecast errors from beginning upto period t
Absolute deviation for period t = Absolute difference between values of ft and At
MAD for period t = Sum of absolute errors for period t starting from period 1 / t
Finally, Tracking signal for period t = RSFEt/ MADt
Week
Demand
Forecast
Forecast error (FE)
RSFE
Absolute deviation
MAD
Tracking signal ( = RSFE/MAD)
1
21
21.00
0.00
0.00
0.00
0.00
0.00
2
21
21.00
0.00
0.00
0.00
0.00
0.00
3
28
21.00
7.00
7.00
7.00
2.33
3.00
4
37
24.85
12.15
19.15
12.15
4.79
4.00
5
26
31.53
-5.53
13.62
5.53
4.94
2.76
6
29
28.49
0.51
14.13
0.51
4.20
3.36
7
37
28.77
8.23
22.36
8.23
4.77
4.68
8
22
33.30
-11.30
11.06
11.30
5.59
1.98
9
24
27.08
-3.08
7.98
3.08
5.31
1.50
10
28
25.39
2.61
10.59
2.61
5.04
2.10
Week
Demand
Forecast
Forecast error (FE)
RSFE
Absolute deviation
MAD
Tracking signal ( = RSFE/MAD)
1
21
21.00
0.00
0.00
0.00
0.00
0.00
2
21
21.00
0.00
0.00
0.00
0.00
0.00
3
28
21.00
7.00
7.00
7.00
2.33
3.00
4
37
24.85
12.15
19.15
12.15
4.79
4.00
5
26
31.53
-5.53
13.62
5.53
4.94
2.76
6
29
28.49
0.51
14.13
0.51
4.20
3.36
7
37
28.77
8.23
22.36
8.23
4.77
4.68
8
22
33.30
-11.30
11.06
11.30
5.59
1.98
9
24
27.08
-3.08
7.98
3.08
5.31
1.50
10
28
25.39
2.61
10.59
2.61
5.04
2.10
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