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Project SchedulingCP - Chapter 10

Lecture3

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Project ManagementProject Management How is it different?

Limited time frame Narrow focus, specific objectives

Why is it used? Special needs Pressures for new or improves products or services

Definition of a project Unique, one-time sequence of activities designed

to accomplish a specific set of objectives in a limited time frame

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Project ManagementProject Management What are the Key Metrics

Time Cost Performance objectives

What are the Key Success Factors? Top-down commitment Having a capable project manager Having time to plan Careful tracking and control Good communications

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Project ManagementProject Management

What are the tools? Work breakdown structure Network diagram Gantt charts Risk management

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Project ManagerProject Manager

Responsible for:

Work QualityHuman Resources TimeCommunications Costs

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Deciding which projects to implement

Selecting a project manager

Selecting a project team

Planning and designing the project

Managing and controlling project resources

Deciding if and when a project should be terminated

Key DecisionsKey Decisions

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Temptation to understate costs

Withhold information

Misleading status reports

Falsifying records

Compromising workers’ safety

Approving substandard work

http://www.pmi.org/

Ethical IssuesEthical Issues

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PERT and CPMPERT and CPM

PERT: Program Evaluation and Review TechniqueCPM: Critical Path Method

Graphically displays project activities Estimates how long the project will take Indicates most critical activities Show where delays will not affect project PERT and CPM have been used to plan, schedule, and control

a wide variety of projects: R&D of new products and processes Construction of buildings and highways Maintenance of large and complex equipment Design and installation of new systems

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PERT/CPMPERT/CPM

PERT/CPM used to plan the scheduling of individual

activities that make up a project. Projects may have as many as several

thousand activities. Complicating factor in carrying out the

activities some activities depend on the completion of

other activities before they can be started.

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PERT/CPMPERT/CPM Project managers rely on PERT/CPM to help them

answer questions such as: What is the total time to complete the project? What are the scheduled start and finish dates for each

specific activity? Which activities are critical?

must be completed exactly as scheduled to keep the project on schedule?

How long can non-critical activities be delayed before they cause an increase in the project completion

time?

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Planning and SchedulingPlanning and Scheduling

Locate new facilities

Interview staff

Hire and train staff

Select and order furniture

Remodel and install phones

Furniture setup

Move in/startup

Activity 0 2 4 6 8 10 12 14 16 18 20

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Project NetworkProject Network

Project network constructed to model the precedence of the

activities. Nodes represent activities Arcs represent precedence relationships of the

activities Critical path for the network

a path consisting of activities with zero slack

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Project Network – An ExampleProject Network – An Example

A

B

C

E

F

Locatefacilities

Orderfurniture

Furnituresetup

Interview

RemodelMove in

D

Hire andtrain

GS

8 weeks

6 weeks

3 weeks

4 weeks9 weeks

11 weeks

1 week

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Management Scientist SolutionManagement Scientist Solution

Path Length (weeks)

Slack

A-B-F-G A-E-G C-D-G

18 20 14

2 0 6

Critical PathCritical Path

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Three-time estimate approach the time to complete an activity assumed to

follow a Beta distribution An activity’s mean completion time is:

t = (a + 4m + b)/6 a = the optimistic completion time estimate b = the pessimistic completion time estimate m = the most likely completion time estimate

An activity’s An activity’s completion time variancecompletion time variance is is 22 = (( = ((bb--aa)/6))/6)22

Uncertain Activity TimesUncertain Activity Times

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Uncertain Activity TimesUncertain Activity Times

In the three-time estimate approach, the critical path is determined as if the mean times for the activities were fixed times.

The overall project completion time is assumed to have a normal distribution with mean equal to the sum of the means along the

critical path, and variance equal to the sum of the variances along the

critical path.

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ActivityImmediate

PredecessorOptimisticTime (a)

Most LikelyTime (m)

PessimisticTime (b)

A -- 4 6 8

B -- 1 4.5 5

C A 3 3 3

D A 4 5 6

E A 0.5 1 1.5

F B,C 3 4 5

G B,C 1 1.5 5

H E,F 5 6 7

I E,F 2 5 8

J D,H 2.5 2.75 4.5

K G,I 3 5 7

ExampleExample

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Management Scientist SolutionManagement Scientist Solution

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Network activities ES: early start EF: early finish LS: late start LF: late finish

Used to determine Expected project duration Slack time Critical path

Key TerminologyKey Terminology

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The Network Diagram (cont’d)The Network Diagram (cont’d) Path

Sequence of activities that leads from the starting node to the finishing node

AON path: S-1-2-6-7 Critical path

The longest path; determines expected project duration Critical activities

Activities on the critical path Slack

Allowable slippage for path; the difference the length of path and the length of critical path

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Network activities ES: early start EF: early finish LS: late start LF: late finish

Used to determine Expected project duration Slack time Critical path

Computing AlgorithmComputing Algorithm

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Advantages of PERTAdvantages of PERT

Forces managers to organize

Provides graphic display of activities

Identifies

Critical activities

Slack activities1

2

3

4

5 6

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Limitations of PERTLimitations of PERT

Important activities may be omitted

Precedence relationships may not be correct

Estimates may include a fudge factor

May focus solely on critical path