In: Statistics and Probability
The sale records of a retail store are given in the Excel worksheet "Retail"
| Week | Value |
| 1 | 10.37 |
| 2 | 5.90 |
| 3 | 8.70 |
| 4 | 6.80 |
| 5 | 7.00 |
| 6 | 9.87 |
| 7 | 10.95 |
| 8 | 10.77 |
| 9 | 11.15 |
| 10 | 8.85 |
| 11 | 13.22 |
| 12 | 6.02 |
| 13 | 6.55 |
| 14 | 9.12 |
| 15 | 11.77 |
| 16 | 10.05 |
| 17 | 10.72 |
| 18 | 9.40 |
| 19 | 9.07 |
| 20 | 12.82 |
| 21 | 4.92 |
| 22 | 10.95 |
| 23 | 13.92 |
| 24 | 15.62 |
| 25 | 6.65 |
| 26 | 13.77 |
| 27 | 8.77 |
| 28 | 9.70 |
| 29 | 8.40 |
| 30 | 10.35 |
| 31 | 8.65 |
| 32 | 6.30 |
| 33 | 6.40 |
| 34 | 9.45 |
| 35 | 9.77 |
| 36 | 5.42 |
| 37 | 10.67 |
| 38 | 7.32 |
| 39 | 7.20 |
| 40 | 7.05 |
| 41 | 9.97 |
| 42 | 7.72 |
| 43 | 10.87 |
| 44 | 7.47 |
| 45 | 13.05 |
| 46 | 9.40 |
| 47 | 12.07 |
| 48 | 10.40 |
| 49 | 6.12 |
| 50 | 12.87 |
| 51 | 12.05 |
| 52 | 12.10 |
| 53 | |
| 54 | |
| 55 |
1. Using the moving average method with p = 3 most recent data, the forecast value at time t = 53 is:
a/ 12.34
b/ 10.50
c/ 11.15
d/ 11.32
2. Using the moving average method with p = 3 most recent data, the M A P E is
a/ 9.52%
b/ 39.23%
c/ 26.92%
d/ 40.45%
3. Using the exponential smoothing with alpha = 4, the smoothed SALE at time t = 10 is
a/ 8.87
b/ 9.81
c/ 12.92
d/ 13.15
4. Using the exponential smoothing with alpha = 4, the forecasted SALE at time t = 53 is
a/ 11.49
b/ 14.50
c/ 11.05
d/ 15.53
5. The value of M A D for using exponential smoothing with alpha = 4 to forecast is
a/ 3.66
b/ 2.29
c/ 4.34
d/ 8.76
| Week | Value | Total for p =3 | Moving avg |
| 1 | 10.37 | ||
| 2 | 5.9 | ||
| 3 | 8.7 | ||
| 4 | 6.8 | 24.97 | 8.323 |
| 5 | 7 | 21.4 | 7.133 |
| 6 | 9.87 | 22.5 | 7.500 |
| 7 | 10.95 | 23.67 | 7.890 |
| 8 | 10.77 | 27.82 | 9.273 |
| 9 | 11.15 | 31.59 | 10.530 |
| 10 | 8.85 | 32.87 | 10.957 |
| 11 | 13.22 | 30.77 | 10.257 |
| 12 | 6.02 | 33.22 | 11.073 |
| 13 | 6.55 | 28.09 | 9.363 |
| 14 | 9.12 | 25.79 | 8.597 |
| 15 | 11.77 | 21.69 | 7.230 |
| 16 | 10.05 | 27.44 | 9.147 |
| 17 | 10.72 | 30.94 | 10.313 |
| 18 | 9.4 | 32.54 | 10.847 |
| 19 | 9.07 | 30.17 | 10.057 |
| 20 | 12.82 | 29.19 | 9.730 |
| 21 | 4.92 | 31.29 | 10.430 |
| 22 | 10.95 | 26.81 | 8.937 |
| 23 | 13.92 | 28.69 | 9.563 |
| 24 | 15.62 | 29.79 | 9.930 |
| 25 | 6.65 | 40.49 | 13.497 |
| 26 | 13.77 | 36.19 | 12.063 |
| 27 | 8.77 | 36.04 | 12.013 |
| 28 | 9.7 | 29.19 | 9.730 |
| 29 | 8.4 | 32.24 | 10.747 |
| 30 | 10.35 | 26.87 | 8.957 |
| 31 | 8.65 | 28.45 | 9.483 |
| 32 | 6.3 | 27.4 | 9.133 |
| 33 | 6.4 | 25.3 | 8.433 |
| 34 | 9.45 | 21.35 | 7.117 |
| 35 | 9.77 | 22.15 | 7.383 |
| 36 | 5.42 | 25.62 | 8.540 |
| 37 | 10.67 | 24.64 | 8.213 |
| 38 | 7.32 | 25.86 | 8.620 |
| 39 | 7.2 | 23.41 | 7.803 |
| 40 | 7.05 | 25.19 | 8.397 |
| 41 | 9.97 | 21.57 | 7.190 |
| 42 | 7.72 | 24.22 | 8.073 |
| 43 | 10.87 | 24.74 | 8.247 |
| 44 | 7.47 | 28.56 | 9.520 |
| 45 | 13.05 | 26.06 | 8.687 |
| 46 | 9.4 | 31.39 | 10.463 |
| 47 | 12.07 | 29.92 | 9.973 |
| 48 | 10.4 | 34.52 | 11.507 |
| 49 | 6.12 | 31.87 | 10.623 |
| 50 | 12.87 | 28.59 | 9.530 |
| 51 | 12.05 | 29.39 | 9.797 |
| 52 | 12.1 | 31.04 | 10.347 |
| 53 | 37.02 | 12.340 |
For moving avg the forecast is calculate by taking sum of preceding 'n' years and then dividing by 'n' where p = n
1. Using the moving average method with p = 3 most recent data, the forecast value at time t = 53 is:
a/ 12.34
b/ 10.50
c/ 11.15
d/ 11.32
| Week | Value | Forecast | Absolute error |value - forecast| |
Percentage error =AE / value |
| 1 | 10.37 | |||
| 2 | 5.9 | |||
| 3 | 8.7 | |||
| 4 | 6.8 | 8.323 | 1.523 | 22.40% |
| 5 | 7 | 7.133 | 0.133 | 1.90% |
| 6 | 9.87 | 7.500 | 2.370 | 24.01% |
| 7 | 10.95 | 7.890 | 3.060 | 27.95% |
| 8 | 10.77 | 9.273 | 1.497 | 13.90% |
| 9 | 11.15 | 10.530 | 0.620 | 5.56% |
| 10 | 8.85 | 10.957 | 2.107 | 23.80% |
| 11 | 13.22 | 10.257 | 2.963 | 22.42% |
| 12 | 6.02 | 11.073 | 5.053 | 83.94% |
| 13 | 6.55 | 9.363 | 2.813 | 42.95% |
| 14 | 9.12 | 8.597 | 0.523 | 5.74% |
| 15 | 11.77 | 7.230 | 4.540 | 38.57% |
| 16 | 10.05 | 9.147 | 0.903 | 8.99% |
| 17 | 10.72 | 10.313 | 0.407 | 3.79% |
| 18 | 9.4 | 10.847 | 1.447 | 15.39% |
| 19 | 9.07 | 10.057 | 0.987 | 10.88% |
| 20 | 12.82 | 9.730 | 3.090 | 24.10% |
| 21 | 4.92 | 10.430 | 5.510 | 111.99% |
| 22 | 10.95 | 8.937 | 2.013 | 18.39% |
| 23 | 13.92 | 9.563 | 4.357 | 31.30% |
| 24 | 15.62 | 9.930 | 5.690 | 36.43% |
| 25 | 6.65 | 13.497 | 6.847 | 102.96% |
| 26 | 13.77 | 12.063 | 1.707 | 12.39% |
| 27 | 8.77 | 12.013 | 3.243 | 36.98% |
| 28 | 9.7 | 9.730 | 0.030 | 0.31% |
| 29 | 8.4 | 10.747 | 2.347 | 27.94% |
| 30 | 10.35 | 8.957 | 1.393 | 13.46% |
| 31 | 8.65 | 9.483 | 0.833 | 9.63% |
| 32 | 6.3 | 9.133 | 2.833 | 44.97% |
| 33 | 6.4 | 8.433 | 2.033 | 31.77% |
| 34 | 9.45 | 7.117 | 2.333 | 24.69% |
| 35 | 9.77 | 7.383 | 2.387 | 24.43% |
| 36 | 5.42 | 8.540 | 3.120 | 57.56% |
| 37 | 10.67 | 8.213 | 2.457 | 23.02% |
| 38 | 7.32 | 8.620 | 1.300 | 17.76% |
| 39 | 7.2 | 7.803 | 0.603 | 8.38% |
| 40 | 7.05 | 8.397 | 1.347 | 19.10% |
| 41 | 9.97 | 7.190 | 2.780 | 27.88% |
| 42 | 7.72 | 8.073 | 0.353 | 4.58% |
| 43 | 10.87 | 8.247 | 2.623 | 24.13% |
| 44 | 7.47 | 9.520 | 2.050 | 27.44% |
| 45 | 13.05 | 8.687 | 4.363 | 33.44% |
| 46 | 9.4 | 10.463 | 1.063 | 11.31% |
| 47 | 12.07 | 9.973 | 2.097 | 17.37% |
| 48 | 10.4 | 11.507 | 1.107 | 10.64% |
| 49 | 6.12 | 10.623 | 4.503 | 73.58% |
| 50 | 12.87 | 9.530 | 3.340 | 25.95% |
| 51 | 12.05 | 9.797 | 2.253 | 18.70% |
| 52 | 12.1 | 10.347 | 1.753 | 14.49% |
| Total | 1319.30% | |||
| MAPE | 26.92% |
Here we ahve forecast for oly 49 values therefore we divide total percentage error by 49.
MAPE = mean absolute percetage error.
2. Using the moving average method with p = 3 most recent data, the M A P E is
a/ 9.52%
b/ 39.23%
c/ 26.92%
d/ 40.45%
| Week | Value | Forecast |
| 1 | 10.37 | 10.37 |
| 2 | 5.9 | 10.37 |
| 3 | 8.7 | 8.58 |
| 4 | 6.8 | 8.63 |
| 5 | 7 | 7.90 |
| 6 | 9.87 | 7.54 |
| 7 | 10.95 | 8.47 |
| 8 | 10.77 | 9.46 |
| 9 | 11.15 | 9.99 |
| 10 | 8.85 | 10.45 |
| 11 | 13.22 | 9.81 |
| 12 | 6.02 | 11.17 |
| 13 | 6.55 | 9.11 |
| 14 | 9.12 | 8.09 |
| 15 | 11.77 | 8.50 |
| 16 | 10.05 | 9.81 |
| 17 | 10.72 | 9.91 |
| 18 | 9.4 | 10.23 |
| 19 | 9.07 | 9.90 |
| 20 | 12.82 | 9.57 |
| 21 | 4.92 | 10.87 |
| 22 | 10.95 | 8.49 |
| 23 | 13.92 | 9.47 |
| 24 | 15.62 | 11.25 |
| 25 | 6.65 | 13.00 |
| 26 | 13.77 | 10.46 |
| 27 | 8.77 | 11.78 |
| 28 | 9.7 | 10.58 |
| 29 | 8.4 | 10.23 |
| 30 | 10.35 | 9.50 |
| 31 | 8.65 | 9.84 |
| 32 | 6.3 | 9.36 |
| 33 | 6.4 | 8.14 |
| 34 | 9.45 | 7.44 |
| 35 | 9.77 | 8.25 |
| 36 | 5.42 | 8.86 |
| 37 | 10.67 | 7.48 |
| 38 | 7.32 | 8.76 |
| 39 | 7.2 | 8.18 |
| 40 | 7.05 | 7.79 |
| 41 | 9.97 | 7.49 |
| 42 | 7.72 | 8.48 |
| 43 | 10.87 | 8.18 |
| 44 | 7.47 | 9.26 |
| 45 | 13.05 | 8.54 |
| 46 | 9.4 | 10.34 |
| 47 | 12.07 | 9.97 |
| 48 | 10.4 | 10.81 |
| 49 | 6.12 | 10.64 |
| 50 | 12.87 | 8.83 |
| 51 | 12.05 | 10.45 |
| 52 | 12.1 | 11.09 |
| 53 | 11.49 |
Since we do not have a forecast for 1st time we equate the forecast to actual. So our forecast will be 1 period later.
Formula:
3. Using the exponential smoothing with alpha =0. 4, the smoothed SALE at time t = 10 is
a/ 8.87
b/ 9.81
c/ 12.92
d/ 13.15
4. Using the exponential smoothing with alpha = 4, the forecasted SALE at time t = 53 is
a/ 11.49
b/ 14.50
c/ 11.05
d/ 15.53
| Week | Value | Forecast | Absolute error (deviation) |
| 1 | 10.37 | 10.37 | 0.000 |
| 2 | 5.9 | 10.37 | 4.470 |
| 3 | 8.7 | 8.58 | 0.118 |
| 4 | 6.8 | 8.63 | 1.829 |
| 5 | 7 | 7.90 | 0.898 |
| 6 | 9.87 | 7.54 | 2.331 |
| 7 | 10.95 | 8.47 | 2.479 |
| 8 | 10.77 | 9.46 | 1.307 |
| 9 | 11.15 | 9.99 | 1.164 |
| 10 | 8.85 | 10.45 | 1.601 |
| 11 | 13.22 | 9.81 | 3.409 |
| 12 | 6.02 | 11.17 | 5.154 |
| 13 | 6.55 | 9.11 | 2.563 |
| 14 | 9.12 | 8.09 | 1.032 |
| 15 | 11.77 | 8.50 | 3.269 |
| 16 | 10.05 | 9.81 | 0.242 |
| 17 | 10.72 | 9.91 | 0.815 |
| 18 | 9.4 | 10.23 | 0.831 |
| 19 | 9.07 | 9.90 | 0.829 |
| 20 | 12.82 | 9.57 | 3.253 |
| 21 | 4.92 | 10.87 | 5.948 |
| 22 | 10.95 | 8.49 | 2.461 |
| 23 | 13.92 | 9.47 | 4.447 |
| 24 | 15.62 | 11.25 | 4.368 |
| 25 | 6.65 | 13.00 | 6.349 |
| 26 | 13.77 | 10.46 | 3.310 |
| 27 | 8.77 | 11.78 | 3.014 |
| 28 | 9.7 | 10.58 | 0.878 |
| 29 | 8.4 | 10.23 | 1.827 |
| 30 | 10.35 | 9.50 | 0.854 |
| 31 | 8.65 | 9.84 | 1.188 |
| 32 | 6.3 | 9.36 | 3.063 |
| 33 | 6.4 | 8.14 | 1.738 |
| 34 | 9.45 | 7.44 | 2.007 |
| 35 | 9.77 | 8.25 | 1.524 |
| 36 | 5.42 | 8.86 | 3.435 |
| 37 | 10.67 | 7.48 | 3.189 |
| 38 | 7.32 | 8.76 | 1.437 |
| 39 | 7.2 | 8.18 | 0.982 |
| 40 | 7.05 | 7.79 | 0.739 |
| 41 | 9.97 | 7.49 | 2.476 |
| 42 | 7.72 | 8.48 | 0.764 |
| 43 | 10.87 | 8.18 | 2.692 |
| 44 | 7.47 | 9.26 | 1.785 |
| 45 | 13.05 | 8.54 | 4.509 |
| 46 | 9.4 | 10.34 | 0.945 |
| 47 | 12.07 | 9.97 | 2.103 |
| 48 | 10.4 | 10.81 | 0.408 |
| 49 | 6.12 | 10.64 | 4.525 |
| 50 | 12.87 | 8.83 | 4.035 |
| 51 | 12.05 | 10.45 | 1.601 |
| 52 | 12.1 | 11.09 | 1.011 |
| Total | 117.207 | ||
| MAD | 2.298 |
MAD = mean aboslute deivation or error
Here since we are forecasting from time period 2 we have 51 pairs of actual and forecast.
5. The value of M A D for using exponential smoothing with alpha = 4 to forecast is
a/ 3.66
b/ 2.29
c/ 4.34
d/ 8.76