Project Management CH9 Project Scheduling

Chapter 9

Project Scheduling: Networks, Duration Estimation, and

Critical Path

09-01

Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Chapter 9 Learning Objectives

After completing this chapter, students will be able to:

Understand and apply key scheduling terminology.

Apply the logic used to create activity networks, including predecessor and successor tasks.

Develop an activity network using Activity-on-Node (AON) techniques.

Perform activity duration estimation based on the use of probabilistic estimating techniques.

09-02


Chapter 9 Learning Objectives

After completing this chapter, students will be able to:

Construct the critical path for a project schedule network using forward and backward passes.

Identify activity float and the manner in which it is determined.

Calculate the probability of a project finishing on time under PERT estimates.

Understand the steps that can be employed to reduce the critical path.

09-03


Project Scheduling Project scheduling requires us to follow some

carefully laid-out steps, in order, for the schedule to take shape.

Project planning, as it relates to the scheduling

process, has been defined by the PMBoK as:

The identification of the project objectives and the ordered activity necessary to complete the project including the identification of resource types and quantities required to carry out each activity or task.

09-04


Project Scheduling Terms

• Successors

• Predecessors

• Network diagram

• Serial activities

• Concurrent activities

09-05

E D

C

B

A F


Project Scheduling Terms

09-06

E D

C

B

A F

• Merge activities

• Burst activities

• Node

• Path

• Critical Path

FIGURE 9.2 Alternative Activity Networks for Term Paper Assignment

Network Diagrams

09-07



AOA Versus AON

The same mini-project is shown with activities on arc…

09-08

C

E D

B F

E

C

D B F

…and activities on node.


Node Labels

09-9

Early Start

Activity Float

Activity Descriptor

Late Start

ID Number

Activity Duration Late Finish

Early Finish

FIGURE 9.4

Activity Node Labels Using MS Project 2010

09-10 Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

FIGURE 9.5

Serial Activities

09-11

Serial activities are those that flow from one to the next, in sequence.


FIGURE 9.6

Activities Linked in Parallel (Concurrent)


When the nature of the work allows for more than one activity to be accomplished at the same time, these activities are called concurrent and parallel project paths are constructed through the network.

FIGURE 9.7

Merge Activity


FIGURE 9.8

Burst Activity


FIGURE 9.10

Complete Activity Network


FIGURE 9.11

Developing the Activity Network Using MS Project 2010


Duration Estimation Methods

• Past experience

• Expert opinion

• Mathematical derivation – Beta distribution

– Most likely (m)

– Most pessimistic (b)

– Most optimistic (a) 4

= TE6

a m bActivity Duration

09-17

2

2 = 6

b aActivity Variance s


FIGURE 9.14 Symmetrical (Normal) Distribution for

Activity Duration Estimation

Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall 09-18

FIGURE 9.15 Asymmetrical (Beta) Distribution for Activity Duration Estimation


Activity Duration and Variance

09-20

Name: Project Delta

Durations are listed in weeks

Activity Description Optimistic Likely Pessimistic

A Contract signing 3 4 11

B Questionnaire design 2 5 8

C Target market ID 3 6 9

D Survey sample 8 12 20

E Develop presentation 3 5 12

F Analyze results 2 4 7

G Demographic analysis 6 9 14

H Presentation to client 1 2 4


Table 9.2


Constructing the Critical Path

• Forward pass – an additive move through the network from start to finish

• Backward pass – a subtractive move through the network from finish to start

• Critical path – the longest path from end to end which determines the shortest project length

09-21


Rules for Forward/Backward Pass Forward Pass Rules (ES & EF)

– ES + Duration = EF

– EF of predecessor = ES of successor

– Largest preceding EF at a merge point becomes EF for successor

Backward Pass Rules (LS & LF) – LF – Duration = LS

– LS of successor = LF of predecessor

– Smallest succeeding LS at a burst point becomes LF for predecessor

09-22

Project Delta Information

09-23

Project Delta

Activity Description Predecessors Estimated Duration

A Contract signing None 5

B Questionnaire design A 5

C Target market ID A 6

D Survey sample B, C 13

E Develop presentation B 6

F Analyze results D 4

G Demographic analysis C 9


Table 9.4

FIGURE 9.16 Partial Project Activity Network with Task Durations


FIGURE 9.18 Activity Network with Forward Pass


FIGURE 9.19 Activity Network with Backward Pass


FIGURE 9.20 Project Network with Activity Slack and Critical Path

Note: Critical path is indicated with bold arrows. 09-27


FIGURE 9.24

AON Network with Laddering Effect



Laddering Activities

Project ABC can be completed more efficiently if subtasks are used

09-29

A(3) B(6) C(9) ABC=18 days

Laddered ABC=12 days

A1(1) A2(1) A3(1)

B1(2) B2(2) B3(2)

C1(3) C2(3) C3(3)

FIGURE 9.25

Example of a Hammock Activity



Reducing the Critical Path

• Eliminate tasks on the CP

• Convert serial paths to parallel when possible

• Overlap sequential tasks

• Shorten the duration on critical path tasks

• Shorten

– early tasks

– longest tasks

– easiest tasks

– tasks that cost the least to speed up 09-31


Summary

1. Understand and apply key scheduling terminology.

2. Apply the logic used to create activity networks, including predecessor and successor tasks.

3. Develop an activity network using Activity-on-Node (AON) techniques.

4. Perform activity duration estimation based on the use of probabilistic estimating techniques.

09-32


Summary

5. Construct the critical path for a project schedule network using forward and backward passes.

6. Identify activity float and the manner in which it is determined.

7. Calculate the probability of a project finishing on time under PERT estimates.

8. Understand the steps that can be employed to reduce the critical path.

09-33

Project Management CH9 Project Scheduling

Education

Transcript of Project Management CH9 Project Scheduling