44578964-PERT-CPM (1)

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A A A A

PERTPERT -- CPMCPM

PERTPERT-- PROGRAM EVALUATION AND REVIEW TECHNIQUEPROGRAM EVALUATION AND REVIEW TECHNIQUE

CPMCPM-- CRITICAL PATH METHODCRITICAL PATH METHOD

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PURPOSES of PERT CPMPURPOSES of PERT CPMTHE MANAGEMENT WILL BE ABLE TO:THE MANAGEMENT WILL BE ABLE TO:

1.1. TO OBTAIN A GRAPHICAL DISPLAY OFTO OBTAIN A GRAPHICAL DISPLAY OF

THE ACTIVITIES OF THE PROJECT ANDTHE ACTIVITIES OF THE PROJECT AND

THUS, BE ABLE TO VISUALIZE ITSTHUS, BE ABLE TO VISUALIZE ITS

ENTIRETY.ENTIRETY.2.2. DETERMINE THE TIME WHEN ADETERMINE THE TIME WHEN A

PARTICULAR PART OF ACTIVITY OF THEPARTICULAR PART OF ACTIVITY OF THE

PROJECT WILL START AND FINISH.PROJECT WILL START AND FINISH.

3.3. DETERMINE THE CRITICAL PATHSDETERMINE THE CRITICAL PATHS

(THOSE THAT MUST NOT BE DELAYED)(THOSE THAT MUST NOT BE DELAYED)

OF THE PROJECT.OF THE PROJECT.

4.4. MONITOR AND CONTROL PROJECTMONITOR AND CONTROL PROJECT

EFFICIENTLY.EFFICIENTLY.

5.5. USE RESOURCES PROPERLY.USE RESOURCES PROPERLY.

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THREE (3) BASIC PHASES OF PMTHREE (3) BASIC PHASES OF PM

BY PERTBY PERT--CPMCPM

1.1. PLANNINGPLANNING

2.2. SCHEDULINGSCHEDULING

3.3. CONTROLLINGCONTROLLING

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TERMINOLOGYTERMINOLOGY

NETWORKNETWORK-- a project in graphicala project in graphicalform. It consist primarily of events andform. It consist primarily of events andactivitiesactivities

ACTIVITIESACTIVITIES-- occur time and presentoccur time and presentthings that must happen to complete athings that must happen to complete aproject.project.

EVENTSEVENTS-- are points in timeare points in timerepresenting the start or completion of representing the start or completion of particular activities.particular activities.

NODENODE-- represents the sequence of represents the sequence of events as they occur and each isevents as they occur and each isnumbered in logical order numbered in logical order

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DUMMY ACTIVITIESDUMMY ACTIVITIES-- are dottedare dottedarrows that indicate logicalarrows that indicate logicalrelationship between different events.relationship between different events.

TIME ESTIMATE (TE)TIME ESTIMATE (TE)-- is the estimatedis the estimated

duration required to accomplish anduration required to accomplish anindividual activity.individual activity.

EARLY START TIME (EST)EARLY START TIME (EST)-- is theis theearliest allowable point in time thatearliest allowable point in time thatany event may occur.any event may occur.

LATE START TIME (LST)LATE START TIME (LST)-- is the latestis the latestallowable point in time that any eventallowable point in time that any eventmay start without delaying the project.may start without delaying the project.

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EARLY FINISH TIME (EFT)EARLY FINISH TIME (EFT)-- is the earliestis the earliestallowable point in time that any event mayallowable point in time that any event maystart without delaying the project.start without delaying the project.

LATE FINISH TIME (LFT)LATE FINISH TIME (LFT)-- is the latestis the latestallowable point in time that any event mayallowable point in time that any event mayfinish without delaying the project.finish without delaying the project.

FLOATFLOAT-- amount of spare time available toamount of spare time available tocomplete an event or activity.complete an event or activity.

MERGE POINTMERGE POINT-- is where more than oneis where more than oneactivity ends in an event.activity ends in an event.

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DIFFERENCE BETWEEN PERT and CPMDIFFERENCE BETWEEN PERT and CPM

PERTPERT CPMCPM

NETWORK DIAGRAMSNETWORK DIAGRAMS

PERT was ³Event oriented´,PERT was ³Event oriented´,i.e., it viewed the project ini.e., it viewed the project in

terms of milestones whichterms of milestones which

had to take place.had to take place.

PERT was geared for PERT was geared for management reportingmanagement reporting

CPM was ³Activity oriented´,CPM was ³Activity oriented´,i.e., it broke the project downi.e., it broke the project down

into activities which need tointo activities which need to

be managedbe managed

CPM having was designed toCPM having was designed to

plan, schedule, and controlplan, schedule, and control

workwork

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PERTPERT CPMCPM

SCHEDULINGSCHEDULING

PERT, dealing with researchPERT, dealing with researchand development useand development use

statistical methods, used asstatistical methods, used as

an expected time estimatean expected time estimate

based on three timebased on three time

estimates, deriving a formulaestimates, deriving a formula

based on Beta distribution.based on Beta distribution.

CPM having been designedCPM having been designedfor construction work, usedfor construction work, used

only one estimate becauseonly one estimate because

there was enough historicalthere was enough historical

data to generate fairlydata to generate fairly

certain duration estimate.certain duration estimate.

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PERTPERT CPMCPM

RESOURCE ANALYSISRESOURCE ANALYSIS

PERT did not extendPERT did not extendbeyond time since it dealt inbeyond time since it dealt in

terms of milestone whichterms of milestone which

do not consume resourcesdo not consume resources

CPM included a practicalCPM included a practicalmethod for analyzing themethod for analyzing the

effect on the cost varyingeffect on the cost varying

project times, including theproject times, including the

ability to handle manpower ability to handle manpower

and equipment resourcesand equipment resources

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HYBRID PERTHYBRID PERT -- CPMCPM

As both systems gained widespread use, modificationsAs both systems gained widespread use, modifications

were introduced to both systems.were introduced to both systems.

In 1961, PERT were adopted the PERT/COST systemIn 1961, PERT were adopted the PERT/COST system

using single time estimate.using single time estimate.

CPM, on the other hand, had borrowed from PERTCPM, on the other hand, had borrowed from PERT

such features as exceptional reporting andsuch features as exceptional reporting and

computerized updating.computerized updating.

What evolved was the Hybrid Technique now referredWhat evolved was the Hybrid Technique now referred

as the PERTas the PERT--CPM.CPM.

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DETERMINATION ANDDETERMINATION AND

CALCULATIONS OF CRITICALCALCULATIONS OF CRITICAL

PATHPATHTo achieve the success of the project,To achieve the success of the project,

analysis of the network is important. Theanalysis of the network is important. The

interaction of different activities in theinteraction of different activities in the

network leads to the determination of thenetwork leads to the determination of the

start and completion time which needstart and completion time which need

computation. The calculations of thecomputation. The calculations of the

completion times are performed directly oncompletion times are performed directly on

the arrow diagram using simple arithmeticthe arrow diagram using simple arithmetic

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TWO METHODS of FINDING theTWO METHODS of FINDING the

CRITICAL PATHCRITICAL PATH

1. a)1. a) BY COMPLETE ENUMERATIONBY COMPLETE ENUMERATION

STEPS:STEPS:

1.1. List all paths leading from the beginningList all paths leading from the beginning

of the project to its end.of the project to its end.2.2. The path with the largest duration is theThe path with the largest duration is the

critical path.critical path.Solution:Solution:

PathPath Total DurationTotal Duration11--22--33--44--55--66--77 7+8+5+7+3=7+8+5+7+3=3030 largest durationlargest duration

11--22--33--66--77 7+8+12+3=227+8+12+3=22

11--22--55--66--77 7+6+4+3=207+6+4+3=20

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TWO METHODS of FINDING theTWO METHODS of FINDING the

CRITICAL PATHCRITICAL PATH

A.A. TIME BOUNDARY METHODTIME BOUNDARY METHOD

STEPS:STEPS:

1.1. Compute the earliest start/finish time of Compute the earliest start/finish time of the project to its end.the project to its end.

2.2. Compute the slack time and determineCompute the slack time and determine

the critical and nonthe critical and non--critical activities.critical activities.

Critical activities have zero slack time.Critical activities have zero slack time.

3.3. Determine the critical pathDetermine the critical path ± ± pathpath

connecting all activities.connecting all activities.

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S AMPLE PROBLEMS AMPLE PROBLEM

1

3

2

5

4

6 7 A

B

C

D

E

F

G

H7

8

5

12

6

4

3

7

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TIME BOUDARY PASSTIME BOUDARY PASS

F orward PassF orward PassPathPath DurationDuration ES ES E F E F

11--22

22--33

22--5533--44

33--66

44--66

55--66

66--77

77

88

6655

1212

77

44

33

00

77

777+8= 157+8= 15

7+8= 157+8= 15

7+8+5= 207+8+5= 20

7+6= 137+6= 13

7+8+5+7= 277+8+5+7= 27

7+8+12=7+8+12=

27max27max

7+6+4= 177+6+4= 17

7

15

1320

27

27

17

30

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TIME BOUDARY PASSTIME BOUDARY PASS

Backward PassBackward Pass

PathPath DurationDuration ES ES E F E F

66--77

55--66

44--66

33--66

33--44

22--5522--33

11--22

33

44

77

1212

55

6688

77

3030

2727

2727

2727

2020

23231515

77

2727

2323

2020

1515

1515

171777

00

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2.2. SOLVING for the SLACK TIMESOLVING for the SLACK TIME

( st= LS ( st= LS ± ± ES)ES)

PathPath DurationDuration LS LS ES ES LS LS - - ES ES

1-2

2-3

2-5

3-4

3-6

4-6

5-6

6-7

7

8

6

5

12

7

4

3

0

7

17

15

15

20

23

27

0

7

7

15

15

20

13

27

0

0

10

0

0

0

10

0

3.3. The critical path is 1The critical path is 1--22--33--44--66--7 and7 and

the critical activities are Athe critical activities are A--BB--DD--GG--HH

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THE COMPUTED CRITICALTHE COMPUTED CRITICAL

PATH NETWORKPATH NETWORK

1

3

2

5

4

6 7 A

B

C

D

E

F

G

H7

8

5

12

6

4

3

7

IT IS NEVER MEANT TO LOOK SIMPLE

SIMPLY BECAUSE WORK IS NEVER SIMPLE.

AT LEAST THIS ALLOWS US TO µSEE¶ THE

WORK GRAPHICALLY.

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44578964-PERT-CPM (1)