case study for forecast
Student+Simple ES
| HBP Product No.: ST5WS | |||||||
| UST005/WSS/1207 | |||||||
| Simple Exponential Smoothing Model | |||||||
| MM-YY | Period | Sales | Forecast | Error | Absolute | Alpha = | 0.4 |
| t | St | Ft | St - Ft | Error | |||
| Jul-09 | 1 | 3,924 | Formula | ||||
| Aug-09 | 2 | 2,619 | 3,924 | -1,304 | 1,304 | F2 = | S1 |
| Sep-09 | 3 | 6,920 | 3,402 | Ft+1 = | Alpha*St + (1 - Alpha)*Ft | ||
| Oct-09 | 4 | 5,676 | Percentage Error = | (St - Ft) / St * 100% | |||
| Nov-09 | 5 | 8,348 | |||||
| Dec-09 | 6 | 6,044 | |||||
| Jan-10 | 7 | 6,877 | |||||
| Feb-10 | 8 | 6,535 | |||||
| Mar-10 | 9 | 6,395 | |||||
| Apr-10 | 10 | 6,684 | |||||
| May-10 | 11 | 5,414 | |||||
| Jun-10 | 12 | 3,180 | |||||
| Jul-10 | 13 | 4,350 | |||||
| Aug-10 | 14 | 3,175 | |||||
| Sep-10 | 15 | 6,935 | |||||
| Oct-10 | 16 | 6,356 | |||||
| Nov-10 | 17 | 8,919 | |||||
| Dec-10 | 18 | 7,146 | |||||
| Jan-11 | 19 | 7,763 | |||||
| Feb-11 | 20 | 7,397 | |||||
| Mar-11 | 21 | 7,286 | |||||
| Apr-11 | 22 | 7,498 | |||||
| May-11 | 23 | 6,386 | |||||
| Jun-11 | 24 | 4,209 | |||||
| Jul-11 | 25 | 4,825 | |||||
| Aug-11 | 26 | 3,764 | |||||
| Sep-11 | 27 | 7,066 | |||||
| Oct-11 | 28 | 7,015 | |||||
| Nov-11 | 29 | 9,535 | |||||
| Dec-11 | 30 | 8,278 | |||||
| Jan-12 | 31 | 8,773 | |||||
| Feb-12 | 32 | 8,393 | |||||
| Mar-12 | 33 | 8,288 | |||||
| Apr-12 | 34 | 8,432 | |||||
| May-12 | 35 | 7,455 | |||||
| Jun-12 | 36 | 5,346 | |||||
| MAD = | |||||||
| This spreadsheet is created by Professor Ronald Lau to accompany the teaching note, Reference No.: UST005/TN/1808 (HBP Product No.: ST5T), of the case : Chinese Pharmaceuticals (HK) Limited: Effective Forecasting for Optimal Inventory Management, Reference No.: UST005/1808 (HBP Product No.: ST5). © 2012 by The Hong Kong University of Science and Technology. This publication may not be digitized, photocopied or otherwise reproduced, posted, or transmitted without the permission of the Hong Kong University of Science and Technology. | |||||||
You should exclude the data of the first two cycles (24months) when calculating the average error (Mean Absolute Deviation), as it takes time for exponential forecasting model to establish before providing an accurate demand forecast
Student+Adaptive ES
| HBP Product No.: ST5WS | ||||||||
| UST005/WSS/1207 | ||||||||
| Adaptive Smoothing Model | ||||||||
| MM-YY | Period | Sales | Forecast | Abolute | % Error | Absolute % | ||
| t | St | Ft | Error | (in dec.) | Error (in dec.) | Formula | ||
| Jul-09 | 1 | 3,924 | F2 = | S1 | ||||
| Aug-09 | 2 | 2,619 | 3,924 | 1,304 | 0.498 | 0.498 | Ft+1 = | Alpha t+1*St + (1-Alpha t+1)*Ft |
| Sep-09 | 3 | 6,920 | 3,274 | Percent Error: PEt = | (St - Ft) / St * 100% | |||
| Oct-09 | 4 | 5,676 | ||||||
| Nov-09 | 5 | 8,348 | Alpha t+1 = | 0.00001, if | PE t | = 0 | ||||
| Dec-09 | 6 | 6,044 | Alpha t+1 = | 0.99999, if | PE t | > 1 | ||||
| Jan-10 | 7 | 6,877 | Alpha t+1 = | | PE t | otherwises | ||||
| Feb-10 | 8 | 6,535 | ||||||
| Mar-10 | 9 | 6,395 | ||||||
| Apr-10 | 10 | 6,684 | ||||||
| May-10 | 11 | 5,414 | ||||||
| Jun-10 | 12 | 3,180 | ||||||
| Jul-10 | 13 | 4,350 | ||||||
| Aug-10 | 14 | 3,175 | ||||||
| Sep-10 | 15 | 6,935 | ||||||
| Oct-10 | 16 | 6,356 | ||||||
| Nov-10 | 17 | 8,919 | ||||||
| Dec-10 | 18 | 7,146 | ||||||
| Jan-11 | 19 | 7,763 | ||||||
| Feb-11 | 20 | 7,397 | ||||||
| Mar-11 | 21 | 7,286 | ||||||
| Apr-11 | 22 | 7,498 | ||||||
| May-11 | 23 | 6,386 | ||||||
| Jun-11 | 24 | 4,209 | ||||||
| Jul-11 | 25 | 4,825 | ||||||
| Aug-11 | 26 | 3,764 | ||||||
| Sep-11 | 27 | 7,066 | ||||||
| Oct-11 | 28 | 7,015 | ||||||
| Nov-11 | 29 | 9,535 | ||||||
| Dec-11 | 30 | 8,278 | ||||||
| Jan-12 | 31 | 8,773 | ||||||
| Feb-12 | 32 | 8,393 | ||||||
| Mar-12 | 33 | 8,288 | ||||||
| Apr-12 | 34 | 8,432 | ||||||
| May-12 | 35 | 7,455 | ||||||
| Jun-12 | 36 | 5,346 | ||||||
| MAD = | ||||||||
| (MAD for last 12 months only) |
You should exclude the data of the first two cycles (24months) when calculating the average error, as it takes time for exponential forecasting model to establish before providing an accurate demand forecast
Student+Full ES
| HBP Product No.: ST5WS | |||||||||||||
| UST005/WSS/1207 | |||||||||||||
| Exponential Smoothing with Trend and Seasonality Model | |||||||||||||
| MM-YY | Period | Sales | Level | Trend | Seasonality | Forecast | Absolute | % Error | Absolute % | ||||
| t | St | Lt | Tt | It | Ft | Error | (in dec.) | Error (in dec.) | |||||
| Jul-09 | 1 | 3,924 | 5718 | 0 | 0.686 | 3,924 | Alpha = | 0.1 | Beta = | 0.2 | Gamma = | 0.15 | |
| Aug-09 | 2 | 2,619 | 5718 | 0 | 0.458 | 2,619 | |||||||
| Sep-09 | 3 | 6,920 | 5718 | 0 | 1.210 | 6,920 | Initialization (1<= t <= 12) Note: This procedure helps determine the initial values of Seasonality for the first year | ||||||
| Oct-09 | 4 | 5,676 | 5718 | 0 | 0.993 | 5,676 | Set | Ft = | St | Tt = | 0 | Lt = | average of first year sales |
| Nov-09 | 5 | 8,348 | 5718 | 0 | 1.460 | 8,348 | It = | St / average of first year sales | |||||
| Dec-09 | 6 | 6,044 | 5718 | 0 | 1.057 | 6,044 | |||||||
| Jan-10 | 7 | 6,877 | 5718 | 0 | 1.203 | 6,877 | Formula (for t>12) | ||||||
| Feb-10 | 8 | 6,535 | 5718 | 0 | 1.143 | 6,535 | |||||||
| Mar-10 | 9 | 6,395 | 5718 | 0 | 1.118 | 6,395 | Lt = | Alpha (St / It-c) + (1 - Alpha) (L t-1 + Tt-1) | |||||
| Apr-10 | 10 | 6,684 | 5718 | 0 | 1.169 | 6,684 | Tt = | Beta (Lt - Lt-1) + (1 - Beta) Tt-1 | |||||
| May-10 | 11 | 5,414 | 5718 | 0 | 0.947 | 5,414 | It = | Gamma (St / Lt) + (1-Gamma) It-c | |||||
| Jun-10 | 12 | 3,180 | 5718 | 0 | 0.556 | 3,180 | |||||||
| Jul-10 | 13 | 4,350 | 5,780 | 12 | 0.696 | 3,924 | F t+m = | ( Lt + (Tt * m) ) * It-c+m | (for m-step-ahead forecast) | ||||
| Aug-10 | 14 | 3,175 | 5,906 | 35 | 0.470 | 2,653 | |||||||
| Sep-10 | 15 | 6,935 | 5,921 | 31 | 1.204 | 7,191 | |||||||
| Oct-10 | 16 | 6,356 | 5,997 | 40 | 1.003 | 5,908 | |||||||
| Nov-10 | 17 | 8,919 | 6,044 | 41 | 1.462 | 8,813 | For F13 to F36: | ||||||
| Dec-10 | 18 | 7,146 | 6,153 | 55 | 1.073 | 6,433 | Ft +1= (Lt+Tt)*It+1-c | ||||||
| Jan-11 | 19 | 7,763 | 6,233 | 60 | 1.209 | 7,466 | e.g. F17= (L16+T16)*I5 | (seasonal cycle c = 12) | |||||
| Feb-11 | 20 | 7,397 | 6,310 | 63 | 1.147 | 7,191 | |||||||
| Mar-11 | 21 | 7,286 | 6,388 | 66 | 1.122 | 7,128 | |||||||
| Apr-11 | 22 | 7,498 | 6,450 | 66 | 1.168 | 7,544 | |||||||
| May-11 | 23 | 6,386 | 6,539 | 70 | 0.951 | 6,169 | |||||||
| Jun-11 | 24 | 4,209 | 6,705 | 89 | 0.567 | 3,675 | |||||||
| Jul-11 | 25 | 4,825 | |||||||||||
| Aug-11 | 26 | 3,764 | |||||||||||
| Sep-11 | 27 | 7,066 | |||||||||||
| Oct-11 | 28 | 7,015 | |||||||||||
| Nov-11 | 29 | 9,535 | |||||||||||
| Dec-11 | 30 | 8,278 | |||||||||||
| Jan-12 | 31 | 8,773 | |||||||||||
| Feb-12 | 32 | 8,393 | |||||||||||
| Mar-12 | 33 | 8,288 | |||||||||||
| Apr-12 | 34 | 8,432 | |||||||||||
| May-12 | 35 | 7,455 | |||||||||||
| Jun-12 | 36 | 5,346 | |||||||||||
| Average Error = | |||||||||||||
You should exclude the data of the first two cycles (24months) when calculating the average error, as it takes time for exponential forecasting model to establish before providing an accurate demand forecast
Student+Inv. Development
| HBP Product No.: ST5WS | ||||||||||
| UST005/WSS/1207 | ||||||||||
| Replenishment Template of Notoginseng Capsules (Lead time = 2 months) | ||||||||||
| Warehouse capacity of inventory | 25,000 | Safety stock = | ||||||||
| MM-YY | Beginning Inventory (Book Record) | Stock to be received in the month | Stock in Transit (to be received in next month) | Inventory Position | Inventory required covering lead time & review period | Order Quantity | Actual Demand | Forecast Demand | Buffer (gift for promotion) | Forecast & Buffer |
| Definition | (=Beg. inv. of last month + stock received - actual demand) | (= Order quantity 2 months ago) | (= Order quantity 1 month ago) | (= Beginning inventory + Stock receipt + Stock in transit) | (= Sum of forecast & buffer for the current month and lead time) | (= Forecast demand over vulnerable period + Safety stock - Inventory position) | Given | Results from Forecast Model | (= forecast*0.2) | (= forecast + buffer) |
| Mar-11 | 26,662 | 0 | 0 | 0 | Legend | 7,286 | 4,813 | |||
| Apr-11 | 0 | 0 | 0 | Order | 7,498 | 4,244 | ||||
| May-11 | 1000 | No need to order | 6,386 | 3,727 | ||||||
| Jun-11 | 4,209 | 3,275 | ||||||||
| Jul-11 | 4,825 | 3,664 | ||||||||
| Aug-11 | 3,764 | 3,569 | ||||||||
| Sep-11 | 7,066 | 7,833 | ||||||||
| Oct-11 | 7,015 | 8,377 | ||||||||
| Nov-11 | 9,535 | 11,224 | ||||||||
| Dec-11 | 8,278 | 8,315 | ||||||||
| Jan-12 | 8,773 | 8,328 | ||||||||
| Feb-12 | 8,393 | 7,616 | ||||||||
| Mar-12 | 8,288 | 7,375 | ||||||||
| Apr-12 | 8,432 | 7,482 | ||||||||
| May-12 | 7,455 | 6,567 | ||||||||
| Jun-12 | 5,346 | 5,033 | ||||||||
| Jul-12 | ||||||||||
| Aug-12 | ||||||||||
| Sep-12 | ||||||||||
| Oct-12 | ||||||||||
| Nov-12 | ||||||||||
| Dec-12 | ||||||||||
| Jan-13 | ||||||||||
| Feb-13 | ||||||||||
| Mar-13 | ||||||||||
| Apr-13 | ||||||||||
| May-13 | ||||||||||
| Jun-13 | ||||||||||