2. PMI defines the scheduling process 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.”
Project scheduling defines the network logic
for all activities that must either precede or
succeed other tasks from the beginning of the
project until its completion.
9/10/2021
2
*
3. Provide a basis for planning and how to use
the resources
Identify the critical path and project
completion time
Identify where slacks (float) are
Reveal interdependencies of activities
Aid in risk analysis (what-if analysis)
9/10/2021
3
*
5. Network scheduling techniques provide a
logical process to consider the order in which
the project activities should occur.
The primary methods for developing project
activity networks are:
Program Evaluation and Review Technique (PERT)
Critical Path Method (CPM) – Also called Arrow Diagram
Method (ADM)
Precedence Diagram Method (PDM)
9/10/2021
5
*
6. There are two ways to show the network:
Activity-On-Node (AON) – nodes represent the activities
Activity-On-Arch (AOA) – archs represent the activities
AON is easier, and it used in commercial
software.
9/10/2021
6
*
8. PERT was developed in the late 1950s in
collaboration between the US Navy, Booz-Allen
Hamilton and Lockeed Corporation for the
creation of the Polaris missile program.
CPM was developed at the same time by
DuPont.
Over the years the differences between
PERT and CPM have blurred, so it is common to
refer these techniques as just PERT/CPM.
9/10/2021
8
*
9. PERT/CPM networks do not allow for leads
and lags between two activities; i.e. a
preceding activity must be completely finished
before the start of the successor activity.
Precedence Diagramming Method (PDM)
allows these leads and lags.
Most project management software systems
use PDM and show interrelationships on bar
charts.
9/10/2021
9
*
11. All activities must be linked to each other
Network diagrams flow from left to right
An activity cannot begin until all preceding
connected activities have been completed
Each activity should have a unique identifier
(number, letter, code, etc.)
Looping is not permitted
It is common to start from a single beginning
and finish on a single ending node
9/10/2021
11
*
12. Define the project and all of its significant
activities
Develop the relationship among activities
Decide which activities must precede others
Draw the network connecting all of the
activities
Compute the longest path which is the
critical path
Calculate activity slacks (float)
Use the network to help plan, schedule, and
control the project
9/10/2021
12
*
13. Nodes representing activities should be
labeled with the following information:
Identifier
Description
Duration
Early Start Time
Early Finish Time
Late Start Time
Late Finish Time
Float
9/10/2021
13
*
15. Early Start (ES) – Earliest possible date an
activity can start based on the network logic
and any schedule constraints.
Early Finish (EF) = ES + Dur
Late Start (LS) – Latest possible date an
activity may begin without delaying a specified
milestone (usually project finish date).
Late Finish (LF) = LS + Dur
9/10/2021
15
*
17. Serial activities flow from one to the next
Concurrent activities are accomplished at
the same time
Merge activities have two or more
immediate predecessor
Burst activities have two or more successor
activities
9/10/2021
17
*
22. 9/10/2021
22
*
Activity Description Predecessors 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
H Presentation to client E, F, G 2
25. Forward pass determines the earliest times
(ES) each activity can begin and the earliest it
can be completed (EF).
There are three steps for applying the
forward pass:
Add all activity times along each path as we move through
the network (ES + Dur = EF)
Carry the EF time to the activity nodes immediately
succeeding the recently completed node. That EF becomes
the ES of the next node, unless the succeeding node is a
merge point
At a merge point, the largest preceding EF becomes the ES
for that node (because the earliest the successor can begin is
when all preceding activities have been completed)
9/10/2021
25
*
26. 9/10/2021
26
*
0 A 5
Contract
5
5 B 10
Design
5
5 C 11
Market ID
6
11 D 24
Survey
13
11 G 20
Demog.
9
24 F 28
Analysis
4
10 E 16
Dev. Present
6
28 H 30
Present
2
Activity D is a merge point for B and C
Activity H is a merge point for E, F, and G
27. The goal of the backward pass is to
determine each activity's Late Start (LS) and
Late Finish (LF) times.
There are three steps for applying the
backward pass:
Subtract activity times along each path through the
network (LF – Dur = LS).
Carry back the LS time to the activity nodes immediately
preceding the successor node. That LS becomes the LF of the
next node, unless the preceding node is a burst point.
In the case of a burst point, the smallest succeeding LS
becomes the LF for that node (because the latest the
predecessor can finish is when any one of the successor
activities should start)
9/10/2021
27
*
28. 9/10/2021
28
*
0 A 5
Contract
0 5 5
5 B 10
Design
6 5 11
5 C 11
Market ID
5 6 11
11 D 24
Survey
11 13 24
11 G 20
Demograph.
19 9 28
24 F 28
Analysis
24 4 28
10 E 16
Dev. Present
22 6 28
28 H 30
Presentation
28 2 30
Activities A, B, and C are burst points
29. Since there exists only one path through the
network that is the longest, the other paths
must either be equal or shorter.
Therefore, there are activities that can be
completed before the time when they are
actually needed.
The time between the scheduled completion
date and the required date to meet critical
path is referred as the slack time.
The activities on the critical path have zero
slack time.
9/10/2021
29
*
30. The use of slack time provides better
resource scheduling.
It is also used as warning sign i.e. if
available slack begins to decrease then activity
is taking longer than anticipated.
Slack time is equal to:
LS – ES or LF – EF
Activities on the critical path have 0 slack;
i.e. any delay in these activities will delay the
project completion.
9/10/2021
30
*
31. 9/10/2021
31
*
0 A 5
0 Contract
0 5 5
5 B 10
1 Design
6 5 11
5 C 11
0 Market ID
5 6 11
11 D 24
0 Survey
11 13 24
11 G 20
8 Demograph.
19 9 28
24 F 28
0 Analysis
24 4 28
10 E 16
12 Dev. Present
22 6 28
28 H 30
0 Presentation
28 2 30
32. 9/10/2021
32
*
Eliminate tasks on the Critical Path
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
33. Lag is the time between Early Start or Early
Finish of one activity and Early Start and Early
Finish on another activity.
For example, in a Finish-to-Start dependency
with a 10-day lag, the successor activity
cannot start until 10 days after the
predecessor activity has finished.
Lags are not the same as slacks. Lags are
between activities whereas slacks are within
activities.
9/10/2021
33
*
34. 9/10/2021
34
*
*Most common type of sequencing
*Shown on the line joining the modes
*Added during forward pass
*Subtracted during backward pass
0 A 6
Spec Design
6
6 B 11
Design Check
5
15 C 22
Blueprinting
7
Lag 4
35. Lead allows an acceleration of the successor
activity. We can expedite the schedule by not
waiting a preceding activity to be completely
finished before starting its successor.
For example, in a Finish-to-Start dependency
with a 10-day lead, the successor activity can
start 10 days before the predecessor activity
has finished.
9/10/2021
35
*
36. 9/10/2021
36
*
Project ABC can be completed more efficiently
if subtasks are used (Fast Tracking)
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)
37. 9/10/2021
37
*
Used as summaries for subsets of activities
0 A 5
0 5 5
5 B 15
5 10 15
15 C 18
15 3 18
0 Hammock 18
0 18 18
Useful with a complex
project or one that has
a shared budget
