Formula
Examples
1) 3 year Exponential Moving Average forecast year | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
Sales | 5.2 | 4.9 | 5.5 | 4.9 | 5.2 | 5.7 | 5.4 | 5.8 | 5.9 | 6 | 5.2 | 4.8 |
Calculate 3 year Exponential Moving Average forecast
Solution:
`alpha=2/(n+1)=2/(3+1)=0.5`
(1) year | (2) Sales | (3) Exponential Smoothing `(alpha=0.5)` |
1 | 5.2 | 5.2 |
2 | 4.9 | `0.5*5.2+0.5*5.2=5.2` |
3 | 5.5 | `0.5*4.9+0.5*5.2=5.05` |
4 | 4.9 | `0.5*5.5+0.5*5.05=5.275` |
5 | 5.2 | `0.5*4.9+0.5*5.275=5.0875` |
6 | 5.7 | `0.5*5.2+0.5*5.0875=5.1438` |
7 | 5.4 | `0.5*5.7+0.5*5.1438=5.4219` |
8 | 5.8 | `0.5*5.4+0.5*5.4219=5.4109` |
9 | 5.9 | `0.5*5.8+0.5*5.4109=5.6055` |
10 | 6 | `0.5*5.9+0.5*5.6055=5.7527` |
11 | 5.2 | `0.5*6+0.5*5.7527=5.8764` |
12 | 4.8 | `0.5*5.2+0.5*5.8764=5.5382` |
13 | | `0.5*4.8+0.5*5.5382=5.1691` |
(1) year | (2) Sales | (3) Exponential Smoothing | (4) Error | (5) |Error| | (6) `"Error"^2` | (7) `|%"Error"|` |
1 | 5.2 | 5.2 | | | | |
2 | 4.9 | 5.2 | | | | |
3 | 5.5 | 5.05 | | | | |
4 | 4.9 | 5.275 | `4.9-5.275=-0.375` | `0.375` | `0.1406` | `7.65%` |
5 | 5.2 | 5.0875 | `5.2-5.0875=0.1125` | `0.1125` | `0.0127` | `2.16%` |
6 | 5.7 | 5.1438 | `5.7-5.1438=0.5562` | `0.5562` | `0.3094` | `9.76%` |
7 | 5.4 | 5.4219 | `5.4-5.4219=-0.0219` | `0.0219` | `0.0005` | `0.41%` |
8 | 5.8 | 5.4109 | `5.8-5.4109=0.3891` | `0.3891` | `0.1514` | `6.71%` |
9 | 5.9 | 5.6055 | `5.9-5.6055=0.2945` | `0.2945` | `0.0867` | `4.99%` |
10 | 6 | 5.7527 | `6-5.7527=0.2473` | `0.2473` | `0.0611` | `4.12%` |
11 | 5.2 | 5.8764 | `5.2-5.8764=-0.6764` | `0.6764` | `0.4575` | `13.01%` |
12 | 4.8 | 5.5382 | `4.8-5.5382=-0.7382` | `0.7382` | `0.5449` | `15.38%` |
13 | | 5.1691 | Total | `3.411` | `1.7648` | `64.19%` |
Forecasting errors
1. Mean absolute error (MAE), also called mean absolute deviation (MAD)
MAE`=1/n sum |e_i|=3.411/9=0.379`
2. Mean squared error (MSE)
MSE`=1/n sum |e_i^2|=1.7648/9=0.1961`
3. Root mean squared error (RMSE)
RMSE`=sqrt(MSE)=sqrt(0.1961)=0.4428`
4. Mean absolute percentage error (MAPE)
MAPE`=1/n sum |e_i/y_i|=64.19/9=7.13`
2) 3 year Exponential Moving Average forecast year | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
Sales | 30 | 25 | 35 | 25 | 20 | 30 | 35 | 40 | 30 | 45 |
Calculate 3 year Exponential Moving Average forecast
Solution:
`alpha=2/(n+1)=2/(3+1)=0.5`
(1) year | (2) Sales | (3) Exponential Smoothing `(alpha=0.5)` |
1 | 30 | 30 |
2 | 25 | `0.5*30+0.5*30=30` |
3 | 35 | `0.5*25+0.5*30=27.5` |
4 | 25 | `0.5*35+0.5*27.5=31.25` |
5 | 20 | `0.5*25+0.5*31.25=28.125` |
6 | 30 | `0.5*20+0.5*28.125=24.0625` |
7 | 35 | `0.5*30+0.5*24.0625=27.0312` |
8 | 40 | `0.5*35+0.5*27.0312=31.0156` |
9 | 30 | `0.5*40+0.5*31.0156=35.5078` |
10 | 45 | `0.5*30+0.5*35.5078=32.7539` |
11 | | `0.5*45+0.5*32.7539=38.877` |
(1) year | (2) Sales | (3) Exponential Smoothing | (4) Error | (5) |Error| | (6) `"Error"^2` | (7) `|%"Error"|` |
1 | 30 | 30 | | | | |
2 | 25 | 30 | | | | |
3 | 35 | 27.5 | | | | |
4 | 25 | 31.25 | `25-31.25=-6.25` | `6.25` | `39.0625` | `25%` |
5 | 20 | 28.125 | `20-28.125=-8.125` | `8.125` | `66.0156` | `40.62%` |
6 | 30 | 24.0625 | `30-24.0625=5.9375` | `5.9375` | `35.2539` | `19.79%` |
7 | 35 | 27.0312 | `35-27.0312=7.9688` | `7.9688` | `63.501` | `22.77%` |
8 | 40 | 31.0156 | `40-31.0156=8.9844` | `8.9844` | `80.719` | `22.46%` |
9 | 30 | 35.5078 | `30-35.5078=-5.5078` | `5.5078` | `30.336` | `18.36%` |
10 | 45 | 32.7539 | `45-32.7539=12.2461` | `12.2461` | `149.9668` | `27.21%` |
11 | | 38.877 | Total | `55.0195` | `464.8548` | `176.22%` |
Forecasting errors
1. Mean absolute error (MAE), also called mean absolute deviation (MAD)
MAE`=1/n sum |e_i|=55.0195/7=7.8599`
2. Mean squared error (MSE)
MSE`=1/n sum |e_i^2|=464.8548/7=66.4078`
3. Root mean squared error (RMSE)
RMSE`=sqrt(MSE)=sqrt(66.4078)=8.1491`
4. Mean absolute percentage error (MAPE)
MAPE`=1/n sum |e_i/y_i|=176.22/7=25.17`
This material is intended as a summary. Use your textbook for detail explanation.
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