Compute mad for the fifth period

Question

Discuss the below:

Q: The manager of a travel agency has been using a seasonally adjusted forecast to predict demand for packaged tours. The actual and predicted values are as follows:

Period	Demand	Predicted
1	139	112
2	194	200
3	165	150
4	91	100
5	90	80
6	132	145
7	126	128
8	134	124
9	95	101
10	149	150
11	100	94
12	85	76
13	123	140
14	134	128

a. Compute MAD for the fifth period, then update it period by period using exponential smoothing with a = .1.

t Period	A Demand	MADt
1	139
2	194
3	165
4	91
5	90
6	132
7	126
8	134
9	95
10	149
11	100
12	85
13	123
14	134

b. Compute a tracking signal for periods 5 through 14 using the initial and updated MADs

t Period	A Demand	Tracking Signal
1	139
2	194
3	165
4	91
5	90
6	132
7	126
8	134
9	95
10	149
11	100
12	85
13	123
14	134