Purchasing, Sales and Operations Planning
Cheat sheet
Forecasting
Moving average:
𝐹𝑡 =
𝐴𝑡−1 + … + 𝐴𝑡−𝑛
𝑛
Weighted moving average:
𝐹𝑡 = 𝜔𝑡−1 𝐴𝑡−1 + … + 𝜔𝑡−𝑛 𝐴𝑡−𝑛
Exponential smoothing:
𝐹𝑡 = (1 − 𝛼)𝐹𝑡−1 +𝛼𝐴𝑡−1
Trend equation:
𝐹𝑡 = 𝑎 + 𝑏𝑡
𝑏 = (𝑛∑𝑡𝑦 − ∑𝑡∑𝑦)/(𝑛∑𝑡 2 − (∑𝑡)2 )
𝑎 = (∑𝑦 − 𝑏∑𝑡)/𝑛
MAD:
∑𝑡 | 𝑒𝑡 |
𝑛
MSE:
∑𝑡 𝑒𝑡 ²
𝑛
MAPE:
|𝑒 |
∑𝑡 𝑡
𝐴𝑡
𝑛
× 100%
AHP criteria comparison scale