In: Economics
Consider the following data:
Year 1 2 3 4 5 6 7 8 9 10 11
Demand 7 9 5 9 13 8 12 13 9 11 7
Starting in year 4 and going to year 12, forecast demand using a 3-year moving average.
(a): What is the predicted value for the next period (Year 12)?
(b): What is the MAD value for this forecast? Starting in year 4 and going to year 12, forecast demand using a 3-year weighted moving average with weights of .1, .3, and .6, using .6 for the most recent year. What is the predicted value for the next period (Year 12)?
(c): What is the predicted value for the next period (Year 12)?
(d): What is the MAD value for this forecast?
Answer
(a)
In order to predict the value for the next period that is 12 th year . As given we have to take 8 year mving average .
So starting fromyear 4 to 12 , we get
Demand in year 12 = sum of demand from year 4 till 11 / number of observations = 9+13+8+12+13+9+11+7 / 8 =82/8 = 10.25 or 10
hence the predicted value for year 12 is 10
(b)
Now calculating the Mean absolute deviation(MAD) we have , the formula
MAD = summation of (xi-x (bar ) / n)
where xi is the individual demand and x(bar is the mean) and n is the no. of observation
So, mean is equal to = 9+13+8+12+13+9+11+7 +10 / 9 = 10.22 or 10
Now constructing the table
xi | xi- x(bar) | mod ( xi-x bar) |
9 | 9-10 = -1 | 1 |
13 | 13-10 =3 | 3 |
8 | 8-10=-2 | 2 |
12 | 12-10 | 2 |
13 | 13-10=3 | 3 |
9 | 9-10=-1 | 1 |
11 | 11-10=1 | 1 |
7 | 7-10=-3 | 3 |
10 | 10-10=0 | 0 |
MAD = (1+3+2+2+3+1+1+3+0)/ 9= 16/9 = 1.77 or 2 (approx)
(c)
So, using weighted moving average we use the formula
Predicted value = most recent period demand * weight assigned / sum of weights
Demand in year 12 = (9*0.1+11*0.3+7*0.6)/(0.1+0.3+0.6) = 8.4/1 =8.4
hence predicted value in year 12 using weighted moving average is 8.4
(d)
mean is equal to = 9+13+8+12+13+9+11+7 +8.4 / 9 =90.4/9 = 10.044 or 10
MAD =
xi | xi- x(bar) | mod ( xi-x bar) |
9 | 9-10 = -1 | 1 |
13 | 13-10 =3 | 3 |
8 | 8-10=-2 | 2 |
12 | 12-10 | 2 |
13 | 13-10=3 | 3 |
9 | 9-10=-1 | 1 |
11 | 11-10=1 | 1 |
7 | 7-10=-3 | 3 |
8.4 | 8.4 -10 = -1.6 | 1.6 |
MAD = (1+3+2+2+3+1+1+3+1.6/9= 17.6/9=1.955 or 2 (approx)
hence MAD is same in both the cases