Components of Demand Average demand for a period of time Trend Seasonal element Cyclical elements Random variation Autocorrelation Session 12-11
McGraw-Hill/Irwin Session 12-11 Components of Demand Average demand for a period of time Trend Seasonal element Cyclical elements Random variation Autocorrelation
Cyclical elements 美国GDP增速 8 ◆GDP增速 6 2 0 -2 螺壁宝墨器离 The GDP Increase Rate of USA,U.S. Census Bureau Session 12-12
McGraw-Hill/Irwin Session 12-12 Cyclical elements The GDP Increase Rate of USA, U.S. Census Bureau 美国GDP增速 -4 -2 0 2 4 6 8 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 GDP增速
Finding Components of Demand Seasonal variation X Linear Trend XX X X X X X 1 2 3 4 Year Session 12-13
McGraw-Hill/Irwin Session 12-13 Finding Components of Demand 12 34 x x x x x x x x x x x xxxx x x x x x x x x x xxx x x x x x x x x x x x x x x x x x x x x Year Sales Seasonal variation Linear Trend
Linear Trend S-Curve Trend 2329576 888 Sales 1.5 Sales (000)1.4 (000 1.3 的 of Demand 0.9 Finding Components 123456789101112 0 10 20 Quarters Time periods Asymptotic Trend Exponential Trend 70 28 60 2.2 Sales (000) 1.6 0.8 10 0.6 0 123456789101112 123456789101112 Quarters Periods ·Sales Trend ·Actual Fitted line Session 12-14
McGraw-Hill/Irwin Session 12-14 of Demand Finding Components
omponents 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) Systematic component:Expected value of demand Random component:The part of the forecast that deviates from the systematic component Forecast error:difference between forecast and actual demand Session 12-15
McGraw-Hill/Irwin Session 12-15 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) • Systematic component: Expected value of demand • Random component: The part of the forecast that deviates from the systematic component • Forecast error: difference between forecast and actual demand