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1、EXAMPLE8.AREA:transportationplanningMETHOD/TECHNIQUE:multipleregressionanalysis—testingproposedlinearmodelswithmorethanoneindependentvariable(whenallvariablesarecontinuous)1.ResearchQuestion/ProblemStatement.Transportationplannersandengineersoftenworkonv
2、ariationsoftheclassic“4-steptransportationplanningprocess”forestimatingtraveldemand.Tripgeneration,thefirststep,generallyinvolvesdevelopingamodelthatcanbeusedtopredictthenumberoftripsoriginating(orending)inazone,whichisageographicalsubdivisionofacorridor
3、,city,orregion(alsoreferredtoasatrafficanalysiszoneorTAZ).Theobjectiveistodevelopastatisticalrelationship(amodel)thatcanbeusedto“explain”thevariationinadependentvariablebasedonthevariationofoneormoreindependentvariables.Inthisparticularapplication,ordina
4、ryleastsquares(OLS)regressionisusedtodevelopamodelbetweentripsgenerated(thedependentvariable)anddemographic,socio-economic,andemploymentvariables(independentvariables)atthehouseholdlevel.Question/Issue:Canalinearrelationship(model)bedevelopedbetweenadepe
5、ndentvariableandoneormoreindependentvariables?Inthisapplication,thedependentvariableisthenumberoftripsproducedbyhouseholdsandindependentvariablesincludepersons,workers,andvehiclesinahousehold,householdincome,andaverageageofthoseinthehousehold.Thebasicque
6、stioniswhethertherelationshipbetweenthedependent(Y)andindependentvariable(s)(Xs)canberepresentedbyalinearmodel:Y=a+b·Xwheretherearetwocoefficients,a,theinterceptandb,theslopeoftheline.Ifthereweremorethanoneindependentvariable,theequationabovewouldsimplyh
7、avemoreterms.Inaddition,inamoreformalpresentation,therewouldalsobeanerrorterm,ε,addedattheendoftheequation.2.IdentificationandDescriptionofVariables.Datafor“4-stepmodeling”oftraveldemandand/orcalibrationofanyspecificmodel(e.g.,tripgeneration)comefromavar
8、ietyofsourcesrangingfromtheUSCensustomail-outortelephonesurveys.Thedatathatarecollectedwilldepend,inpart,onthespecificpurposeofthemodelingeffort.Dataappropriateforatripgenerationmodelaretypicallycollectedfromsomesortofhous
