Project management a managerial approach chapter 08
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Project Management: A
Managerial Approach
Chapter 8 – Scheduling
© 2006 John Wiley
Overview
•
•
•
•
WBS to Schedule Process
PERT
Schedule Types
CPM
© 2006 John Wiley
Scheduling
• A schedule is the conversion of a project
action plan into an operating timetable
• It serves as the basis for monitoring and
controlling project activity
• Taken together with the plan and budget,
it is probably the major tool for the
management of projects
© 2006 John Wiley
Chapter 8-1
Simple Schedule – Gantt Chart
© 2006 John Wiley
Network Techniques: PERT and CPM
• With the exception of Gantt charts, the most
common approach to scheduling is the use of
network techniques such as PERT and CPM
• The Program Evaluation and Review Technique
(PERT) was developed by the U.S. Navy in 1958
• The Critical Path Method (CPM) was developed
by DuPont, Inc during the same time period
© 2006 John Wiley
Chapter 8-7
Scheduling Terminology
• Activity - A specific task or set of tasks that are
required by the project, use up resources, and take
time to complete
• Event - The result of completing one or more
activities. An identifiable end state occurring at a
particular time. Events use no resources.
• Network - The combination of all activities and
events define the project and the activity
precedence relationships
© 2006 John Wiley
Chapter 8-9
Scheduling Terminology
• Path - The series of connected activities (or
intermediate events) between any two events
in a network
• Critical - Activities, events, or paths which, if
delayed, will delay the completion of the
project. A project’s critical path is understood
to mean that sequence of critical activities that
connect the project’s start event to its finish
event
© 2006 John Wiley
Chapter 8-10
Scheduling Terminology
• An activity can be in any of these conditions:
– It may have a successor(s) but no predecessor(s) starts a network
– It may have a predecessor(s) but no successor(s) ends a network
– It may have both predecessor(s) and successor(s) - in
the middle of a network
• Interconnections from horizontal links in vertical
WBS
© 2006 John Wiley
Hypothetical Network
3
13
1
30
16
2
5
20
6
4
Calculate t(e) and Z for this network……
© 2006 John Wiley
5
6
TE=64
Activity and Project Frequency Distributions
ACTIVITY
a
PROJECT
m
b
(A)
© 2006 John Wiley
TE
(B)
PERT Activity Calculation
t(e) = a + 4m + b
6
a = Most Optimistic (MO)
m = Most Likely (ML)
b = Most Pessimistic (MP)
t(e) = Activity Duration
When a single estimate for activity time is not sufficient!
© 2006 John Wiley
PERT Schedule Probability
Z = T(S) – T(E)
SD(T[E])2
Z = Probability of
Meeting Schedule
T(S) = Scheduled Duration
T(E) = Critical Path Duration
Z is derived from a table of predetermined probabilities
© 2006 John Wiley
PERT Activity Times & Variances
Activity
a
m
b
1-2
17
29
47
2-3
6
12
24
2-4
16
19
28
3-5
13
16
19
4-5
2
5
14
5-6
2
5
8
© 2006 John Wiley
t(e)
Variance of Activity Estimates
Activity
a
m
b
t(e)
1-2
17
29
47
30
2-3
6
12
24
13
2-4
16
19
28
20
3-5
13
16
19
16
4-5
2
5
14
6
5-6
2
5
8
6
© 2006 John Wiley
[(b-a)/6]2
Var
Possible Project Durations
TS=67
TE=64
© 2006 John Wiley
Z Table
Z Value
Probability
Z Value
Probability
-2.0
0.02
+2.0
0.98
-1.5
0.07
+1.5
0.93
-1.0
0.16
+1.0
0.84
-0.7
0.24
+0.7
0.76
-0.5
0.31
+0.5
0.69
-0.3
0.38
+0.3
0.62
-0.1
0.36
+0.1
0.54
© 2006 John Wiley
Gantt Charts
• The Gantt chart shows planned and actual progress
for a number of tasks displayed against a horizontal
time scale
• It is an effective and easy-to-read method of
indicating the actual current status for each set of
tasks compared to the planned progress for each item
of the set
• It can be helpful in expediting, sequencing, and
reallocating resources among tasks
• Gantt charts usually do not show technical
dependencies
© 2006 John Wiley
Chapter 8-14
Drawing Networks
• Activity-on-Arrow (AOA) networks use arrows to
represent activities while nodes stand for events
• Activity-on-Node (AON) networks use nodes to
represent activities with arrows to show
precedence relationships
• The choice between AOA and AON
representation is largely a matter of personal
preference
© 2006 John Wiley
Chapter 8-12
Hypothetical Network
3
1
2
5
4
© 2006 John Wiley
6
AOA Network Building Blocks
Activity
79
Install software
© 2006 John Wiley
Event
80
Partial Koll Business Center - AOA
1
A
Application
approval
2
B
Construction
plans
4
C
Traffic
study
D
Service
availability
check
3
© 2006 John Wiley
5
Partial AOA Network
3
X
1
A
C
2
1
3
2
1
2
4
(B)
4
C
X
E
X
C
B
A
4
(A)
B
A
B
3
(C)
© 2006 John Wiley
E
E
Partial AOA Network
4
B
A
1
X
C
2
E
3
D
(D)
B
1
A
2
C
4
X
3
D
(E)
© 2006 John Wiley
5
E
?
5
F
Full AOA Network
B
15 X
1
A
5
Legend
Activity
Duration
2
C
10
3
4
0
0
Y
5
E
15
F
10
D
5
© 2006 John Wiley
6
G
170
7
H
35
KOLL BUSINESS CENTER
County Engineers Design Department
8
Activity-on-Node Network Fundamentals
J, K, & L can all begin at
the same time, if you wish
(they need not occur
simultaneously)
J
A
B
C
K
A is preceded by nothing
B is preceded by A
C is preceded by B
L
(A)
M
(C)
but
All (J, K, L) must be
completed before M can
begin
Y
Y and Z are preceded by X
X
Z
Z is preceded by X and Y
Z
Y and Z can begin at the
same time, if you wish
Y
AA
AA is preceded by X and Y
X
(B)
(D)
© 2006 John Wiley
