Multiplicative Seasonal InfluencesYear 1Year 2Year 3Year 4Quarter145/250=0.1870/300=0.23100/450=0.22100/550=0.182335/250=1.34370/300=1.23585/450=1.30725/550=1.323520/250=2.08590/300=1.97830/450=1.841160/550=2.114100/250=0.40170/300=0.57285/450=0.63215/550=0.39Multiplicative influenceStep 1: For each period, computeActual Quarterly DemandSeasonal index :Average Quarterly DemandFor example, seasonal Index, Year 1, Quarter 1=
Quarter Year 1 Year 2 Year 3 Year 4 1 45/250 = 0.18 70/300 = 0.23 100/450 = 0.22 100/550 = 0.18 2 335/250 = 1.34 370/300 = 1.23 585/450 = 1.30 725/550 = 1.32 3 520/250 = 2.08 590/300 = 1.97 830/450 = 1.84 1160/550 = 2.11 4 100/250 = 0.40 170/300 = 0.57 285/450 = 0.63 215/550 = 0.39 Multiplicative Seasonal Influences For example, seasonal Index, Year 1, Quarter 1 = Seasonal index = Actual Quarterly Demand Average Quarterly Demand Step 1: For each period, compute Multiplicative influence:
Multiplicative Seasonal InfluencesYear 1Year 2QuarterYear 3Year 4145/250=0.1870/300=0.23100/450=0.22100/550=0.182335/250=1.34370/300=1.23585/450=1.30725/550=1.323520/250=2.08590/300=1.97830/450=1.841160/550=2.114100/250=0.40170/300=0.57285/450=0.63215/550=0.39QuarterAverageSeasonalIndexStep 2: For1each quarter2computethe3average4seasonal index
Quarter Year 1 Year 2 Year 3 Year 4 1 45/250 = 0.18 70/300 = 0.23 100/450 = 0.22 100/550 = 0.18 2 335/250 = 1.34 370/300 = 1.23 585/450 = 1.30 725/550 = 1.32 3 520/250 = 2.08 590/300 = 1.97 830/450 = 1.84 1160/550 = 2.11 4 100/250 = 0.40 170/300 = 0.57 285/450 = 0.63 215/550 = 0.39 Quarter Average Seasonal Index 1 2 3 4 Multiplicative Seasonal Influences Step 2: For each quarter compute the average seasonal index
Multiplicative Seasonal InfluencesThe average seasonal indices can be used to get forecastsof the quarterly demands if the average quarterly demand isprojected. The quarterly demand forecast of a quarter =projected average quarterly demand x average seasonalindex of that quarter.For example, suppose that the next year, in Year 5The projected annual demand is 2600. So, the projectedaverage quarterly demand is 2600/4=650.Then, the demand forecast in Quarter 1 = 650(0.20)=130. Thenext slide shows the demand forecast for the other quarters
Multiplicative Seasonal Influences The average seasonal indices can be used to get forecasts of the quarterly demands if the average quarterly demand is projected. The quarterly demand forecast of a quarter = projected average quarterly demand average seasonal index of that quarter. For example, suppose that the next year, in Year 5, The projected annual demand is 2600. So, the projected average quarterly demand is 2600/4=650. Then, the demand forecast in Quarter 1 = 650(0.20)=130. The next slide shows the demand forecast for the other quarters
Multiplicative Seasonal InfluencesGiven projected average quarterly demand =650The quarterly demand forecasts are obtained as follows:QuarterAverage Seasonal IndexForecast1234
Multiplicative Seasonal Influences Given projected average quarterly demand =650 The quarterly demand forecasts are obtained as follows: Quarter Average Seasonal Index Forecast 1 2 3 4
Additive SeasonallnfluencesYear 1Year 2Year 3Year 4Quarter145-250=-20570-300=-230100-450=-350100-550=-4502335-250=85370-300=70585-450=135725-550=1753520-250=270590-300=290830-450=3801160-550=6104100-250=-150170-300=-130285-450=-165215-550=-335Additiveinfluence:Step 1: For each period, compute seasonal index= Actual Quarterly Demand - Average Quarterly DemandForexample, seasonal Index, Year 1,Quarter 1=45-250=-205
Additive Seasonal Influences For example, seasonal Index, Year 1, Quarter 1 = 45-250 = -205 = Actual Quarterly Demand - Average Quarterly Demand Step 1: For each period, compute seasonal index Additive influence: Quarter Year 1 Year 2 Year 3 Year 4 1 45-250 = -205 70-300 = -230 100-450 = -350 100-550 = -450 2 335-250 = 85 370-300 = 70 585-450 = 135 725-550 = 175 3 520-250 = 270 590-300 = 290 830-450 = 380 1160-550 = 610 4 100-250 = -150 170-300 = -130 285-450 = -165 215-550 = -335