demand forecasting for inventory control promotion forecasts

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1、Chapter6PromotionForecasts6.1IntroductionPromotionscomeinvariousways:pricereduction,buyonegetonefree,zerointerest,nomoneydown,andsoon.Theyoftenoccurwhenasupplierorastocklocationoffersapriceincentiveofsomesorttothecustomerstobuynowwithenticementsforpurchasesmoreoftenorinlargerquantities

2、.Thepromotiontypi-callyhasastart-dateandend-date,andthedemandduringthesedaysisrelativelyhigherthanthenormalnon-promodays.Thissituationcauseswildfluctuationsinthedemandhistoryandupsetstheforecastingmodelinuse.Thestandarddevi-ationincreasesandtheforecastcoefficientsswingoutofnormalcontro

3、l.Specialadjustmentsareneededintheforecastmodelstoovercomethefluctuations.Twoforecastmodelsaredescribedheretoaccommodatethepromotionactivity:thepromotionhorizontalmodelandthepromotiontrendmodel.Bothofthemodelsinvolvetwostages:theinitialstageandtherevisionstage.Theinitialstageisthefirst

4、estimatesofthecoefficientsofthemodel.ThisstagerequiresNhistorymonthsofdemandsandpromotionmeasures.Thecoefficientsofthemodelareestimatedusingregressionmethodswhereequalweightisgiventoeachofthehistorymonths.Therevisionstageisusedforthemonthsaftertheinitialstagewherethecoefficientsarerevi

5、sedeverymonthwitheachcurrentmonth’sdatausingthesmoothingmethod.Estimatesofthestandarddeviationandthecoef-ficientofvariationarecomputedforeachofthetwostages.6.2PromotionHorizontalModelThepromotionhorizontalmodelisbasedonthemostrecentNmonthsofdemandandpromotionhistory.Thedemandsaredenote

6、dasx(t)andthepromotionsarep(t)fort=1toN,wheret=1istheoldestmonthandt=Nisthemostcurrentmonth.Themodelisofthefollowingform:©SpringerInternationalPublishingSwitzerland201571N.T.Thomopoulos,DemandForecastingforInventoryControl,DOI10.1007/978-3-319-11976-2_6726PromotionForecastsf(t)=+acp(t)

7、wheref(t)isthefittedvalueathistorymontht,andp(t)isthecorrespondingpromo-tionmeasureatt.Thepromotion,p(t),couldbeameasureoftheportionofmonthtthatisactivewithapromotion.Thetwocoefficientsare(a,c),wherea,istheestimateofthelevel,andcisthepromocoefficient.Toapply,themodelrequirestwostages