Project Scheduling: Networks, Duration Estimation, and Critical
Path 09-01
Slide 2
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
Slide 3
Copyright 2013 Pearson Education, Inc. Publishing as Prentice
Hall 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
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Copyright 2013 Pearson Education, Inc. Publishing as Prentice
Hall 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
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Copyright 2013 Pearson Education, Inc. Publishing as Prentice
Hall Project Scheduling Terms Successors Predecessors Network
diagram Serial activities Concurrent activities E D C B A F
09-05
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Copyright 2013 Pearson Education, Inc. Publishing as Prentice
Hall Project Scheduling Terms E D C B A F Merge activities Burst
activities Node Path Critical Path 09-06
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FIGURE 9.2 Alternative Activity Networks for Term Paper
Assignment Network Diagrams Copyright 2013 Pearson Education, Inc.
Publishing as Prentice Hall 09-07
Slide 8
Copyright 2013 Pearson Education, Inc. Publishing as Prentice
Hall AOA Versus AON The same mini-project is shown with activities
on arc C E D B F E C D B F and activities on node. 09-08
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Copyright 2013 Pearson Education, Inc. Publishing as Prentice
Hall Node Labels Early Start Activity Float Activity Descriptor
Late Start ID Number Activity DurationLate Finish Early Finish
09-9
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FIGURE 9.4 Activity Node Labels Using MS Project 2010 09-10
Copyright 2013 Pearson Education, Inc. Publishing as Prentice
Hall
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FIGURE 9.5 Serial Activities Serial activities are those that
flow from one to the next, in sequence. 09-11 Copyright 2013
Pearson Education, Inc. Publishing as Prentice Hall
Slide 12
FIGURE 9.6 Activities Linked in Parallel (Concurrent) 09-12
Copyright 2013 Pearson Education, Inc. Publishing as Prentice Hall
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.
Slide 13
FIGURE 9.7 Merge Activity 09-13 Copyright 2013 Pearson
Education, Inc. Publishing as Prentice Hall
Slide 14
FIGURE 9.8 Burst Activity Copyright 2013 Pearson Education,
Inc. Publishing as Prentice Hall 09-14
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FIGURE 9.10 Complete Activity Network Copyright 2013 Pearson
Education, Inc. Publishing as Prentice Hall 09-15
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FIGURE 9.11 Developing the Activity Network Using MS Project
2010 09-16 Copyright 2013 Pearson Education, Inc. Publishing as
Prentice Hall
Slide 17
Duration Estimation Methods Past experience Expert opinion
Mathematical derivation Beta distribution Most likely (m) Most
pessimistic (b) Most optimistic (a) Copyright 2013 Pearson
Education, Inc. Publishing as Prentice Hall 09-17
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FIGURE 9.14 Symmetrical (Normal) Distribution for Activity
Duration Estimation Copyright 2013 Pearson Education, Inc.
Publishing as Prentice Hall 09-18
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FIGURE 9.15 Asymmetrical (Beta) Distribution for Activity
Duration Estimation Copyright 2013 Pearson Education, Inc.
Publishing as Prentice Hall 09-19
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Activity Duration and Variance 09-20 Copyright 2013 Pearson
Education, Inc. Publishing as Prentice Hall Table 9.2
Slide 21
Copyright 2013 Pearson Education, Inc. Publishing as Prentice
Hall 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
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Copyright 2013 Pearson Education, Inc. Publishing as Prentice
Hall 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
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Project Delta Information 09-23 Copyright 2013 Pearson
Education, Inc. Publishing as Prentice Hall Table 9.4
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FIGURE 9.16 Partial Project Activity Network with Task
Durations Copyright 2013 Pearson Education, Inc. Publishing as
Prentice Hall 09-24
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FIGURE 9.18 Activity Network with Forward Pass 09-25 Copyright
2013 Pearson Education, Inc. Publishing as Prentice Hall
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FIGURE 9.19 Activity Network with Backward Pass 09-26 Copyright
2013 Pearson Education, Inc. Publishing as Prentice Hall
Slide 27
FIGURE 9.20 Project Network with Activity Slack and Critical
Path Note: Critical path is indicated with bold arrows. 09-27
Copyright 2013 Pearson Education, Inc. Publishing as Prentice
Hall
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FIGURE 9.24 AON Network with Laddering Effect 09-28 Copyright
2013 Pearson Education, Inc. Publishing as Prentice Hall
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Laddering Activities Project ABC can be completed more
efficiently if subtasks are used A(3)B(6)C(9) ABC=18 days Laddered
ABC=12 days A 1 (1)A 2 (1)A 3 (1) B 1 (2)B 2 (2)B 3 (2) C 1 (3)C 2
(3)C 3 (3) 09-29
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FIGURE 9.25 Example of a Hammock Activity 09-30 Copyright 2013
Pearson Education, Inc. Publishing as Prentice Hall
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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
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Copyright 2013 Pearson Education, Inc. Publishing as Prentice
Hall 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
Slide 33
Copyright 2013 Pearson Education, Inc. Publishing as Prentice
Hall 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
Slide 34
Copyright 2013 Pearson Education, Inc. Publishing as Prentice
Hall 09-34
