Planning Demand and Supply in a Supply Chain

Forecasting and Aggregate Planning

供應鏈的需求預測

供應鏈決策的階層界定需求預測的要項時間數列預測法估算預測的誤差

Learning ObjectivesPhases of supply chain decisions

Identify components of a demand forecast

Time series forecasting

Estimate forecast error

供應鏈決策的階層Phases of Supply Chain Decision

s策略性 Strategy or design: 預測 Forecast

計畫性 ( 戰術性 )Planning:預測 Forecast

作業性 Operation 實際需求 Actual demand

Characteristics of forecasts

Forecasts are always wrong. Should include expected value and measure of error.Long-term forecasts are less accurate than short-term forecasts: Forecast horizonAggregate forecasts are more accurate than disaggregate forecasts

Forecasting Methods

Qualitative

Time SeriesStatic Adaptive

Causal

Simulation

Components of an observation

Observed demand (O) =

Systematic component (S) + Random component (R)

Level (current deseasonalized demand)

Trend (growth or decline in demand)

Seasonality (predictable seasonal fluctuation)

Time Series Forecasting

Quarter Demand Dt II, 1998 8000 III, 1998 13000 IV, 1998 23000 I, 1999 34000 II, 1999 10000 III, 1999 18000 IV, 1999 23000 I, 2000 38000 II, 2000 12000 III, 2000 13000 IV, 2000 32000 I, 2001 41000

Forecast demand for thenext four quarters.

Time Series Forecasting

0

10,000

20,000

30,000

40,000

50,000

97,2

97,3

97,4

98,1

98,2

98,3

98,4

99,1

99,2

99,3

99,4

00,1

Forecasting methodsStatic Ft+l =[ L + (t+l)T ] St+l

AdaptiveFt+l =[ Lt + lTt ] St+l

Moving averageSimple exponential smoothingHolt’s model (with trend)Winter’s model (with trend and seasonalit

y)Excel File

Error measures

MAD

Mean Squared Error (MSE)

Mean Absolute Percentage Error (MAPE)

Bias

Tracking Signal