SAMSUDINAHMADFacultyofGeoinformation andRealEstate

Universiti Teknologi Malaysia@Mail:samsudin@utm.my

Topic5PERTANDCPMNETWORKS

History

• Late1950s– ProgramEvaluationandReviewTechnique(PERT)

• U.S.Navy,Booz‐AllenHamilton,andLockeheedAircraft

• Probabilisticactivitydurations– CriticalPathMethod(CPM)

• DupontDeNemoursInc.• Deterministicactivitydurations

TheLanguageofPERT/CPM

• Activity– taskorsetoftasks– useresources

• Event– stateresultingfromcompletionofoneormoreactivities

– consumenoresourcesortime– predecessoractivitiesmustbecompleted

TheLanguageofPERT/CPMcontinued

• Milestones– eventsthatmarksignificantprogress

• Network– diagramofnodesandarcs– usedtoillustratetechnologicalrelationships

• Path– seriesofconnectedactivitiesbetweentwoevents

TheLanguageofPERT/CPMconcluded

• CriticalPath– setofactivitiesonapaththatifdelayedwilldelaycompletionofproject

• CriticalTime– timerequiredtocompleteallactivitiesonthecriticalpath

BuildingtheNetwork

SampleSetofProjectActivitiesandPrecedences

Task Predecessora --

b --

c a

d b

e b

f c, d

g e

Stage1ofaSampleAONNetwork

Stage2ofaSampleAONNetwork

ACompletedSampleAONNetwork

Stage1ofaSampleAOANetwork

Stage2ofaSampleAOANetwork

ACompletedSampleAOANetwork

ACompletedSampleAOANetworkShowingtheUseofaDummyTask

SampleProblemforFindingtheCriticalPathandCriticalTime

Activity Predecessor Duration

a -- 5 daysb -- 4c a 3d a 4e a 6f b, c 4g d 5h d, e 6i f 6j g, h 4

Stage1ofaSampleNetwork

ACompleteNetwork

InformationContentsinanAONNode

TheCriticalPathandTimeforSampleProject

CalculatingActivitySlack

• SlackorFloatLST‐ EST=LFT‐ EFT=Slack

AnMSPVersionofPERT/CPMNetwork

AModifiedVersionofMSPNetwork

PROJECTUNCERTAINTYANDRISKMANAGEMENT

CalculatingProbabilisticActivityTimes• ThreeTimeEstimates

– pessimistic(a)– mostlikely(m)– optimistic(b)

TheStatisticalDistributionofallPossibleTimesforanActivity

ActivityExpectedTimeandVariance

22

E

6)(Var

6)(

6)4(T

ab

ab

bma

95PercentLevel

• Taskwillbea orlower5percentofthetime

• Taskwillbeb orgreater5percentofthetime

3.3)( ab

90PercentLevel

• Taskwillbea orlower10percentofthetime

• Taskwillbeb orgreater10percentofthetime

6.2)( ab

95PercentLevel(AlternativeInterpretation)• Taskwillbebetweenaandb95percentofthetime

92.3)( ab

90PercentLevel(AlternativeInterpretation)• Taskwillbebetweenaandb90percentofthetime

29.3)( ab

AnAONNetwork

AnMSPVersionofaSampleProblemNetwork

APert/CPMNetworkfortheDayCareProject

AnMSPCalendarfortheDayCareProject,4/16/00to5/27/00

TheProbabilityofCompletingtheProjectonTime

2

)(

DZ

=NORMDIST(D,,,TRUE)

TheStatisticalDistributionofCompletionTimesofthePatha‐b‐d‐g‐h

SelectingRiskandFindingD

2 ZD

NORMINV (probability, , , TRUE)

SIMULATION

MEM 612 Project Management

TraditionalStatisticsVersusSimulation• Similarities

– mustenumeratealternatepaths

• Differences– simulationdoesnotrequireassumptionofpathindependence

THEGANNTCHART

AGanttChartofaSampleProject

AGanttChartofSampleProjectShowingCriticalPath,PathConnections,Slack,EST,LST,EFT,andLFT

AGanttChartofaDayCareProjectShowingExpectedDurations,CriticalPath,Milestone,andResourceRequirements

AProgressReportonaDayCareProjectShowingActualProgressVersusBaseline

EXTENSIONSTOPERT/CPM

PrecedenceDiagramming

Finish‐to‐startlinkage

Start‐to‐startlinkage

Finish‐to‐finishlinkage

Start‐to‐finishlinkage

PrecedenceDiagrammingConventions

OtherMethods

• GraphicalEvaluationandReviewTechnique(GERT)– combinesflowgraphs,probabilisticnetworks,anddecisiontrees

– allowsloopsbacktoearliereventsandprobabilisticbranching

Reference

• Meredith,R.J.&Mantel,J.S.(1995).ProjectManagement– AManagerialApproach.JohnWiley&Sons,5thEdition.