Transcript Project Management and Scheduling

Project Scheduling
Project Management 517
Chapter 8
Prof. M. Anvari
http://www.anvari.net/project_management.htm
Scheduling
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Scheduling Defined
Gantt Charts
Network Techniques: PERT and CPM
Determining Task Durations
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Probability and Simulation
Some Examples
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Scheduling Defined
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The conversion of a project action plan
into an operating timetable
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Serves as the basis for monitoring and
controlling the project
A major tool for the management of
projects
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Scheduling
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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
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8-4
Some Benefits of Successful
Scheduling
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Illustrates interdependence of all tasks
Identifies times when resources must be
available
Facilitates communication throughout the
project
Determines critical activities/critical path
Affects client expectations through
establishment of activities, milestones, and
completion dates
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A Process for Scheduling
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1. Think
2. List activities
3. Arrange activities considering precedence
and relationships
4. Develop Gantt charts and PERT/CPM
networks
5. Determine critical activities/critical path
6. Crash and adjust as necessary
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Gantt Charts
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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
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JAN
Gantt Charts
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MAR
8 15 22 29 5 12 19 26 5 12 19 26
Advantages
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1
FEB
Easy to understand
Easy to show progress and status
Easy to maintain
Most popular view to communicate project status
to client and/or senior management
Disadvantages
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Can be superficial
Not always easy to see precedence, relationships
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Network Techniques: PERT and CPM
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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
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Scheduling Terminology
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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
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Scheduling Terminology
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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
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Scheduling Terminology
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An activity can be in any of these conditions:
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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
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PERT/CPM Network Charts
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Advantages
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Allows visualization of task relationships
Facilitates calculation of critical path
Clarifies impact of decisions on downstream
activities
Disadvantages
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Complex, not easy to comprehend at a glance
Charts don’t readily depict durations, dates,
progress
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Look at a Simple Network, for
a Simple Project
Duration
(weeks)
Activity
Predecessor
A
14
Start
B
3
Start
C
3
A,B
D
7
B
E
4
C,D
F
10
E
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Drawing Networks
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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
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AOA Network Building Blocks
Activity
79
Event
Install software
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8-23
Activity-on-Node Network Fundamentals
J
A
B
C
K
A is preceded by nothing
B is preceded by A
C is preceded by B
L
(A)
M
(C)
J, K, & L can all begin at
the same time, if you wish
(they need not occur
simultaneously)
but
All (J, K, L) must be
completed before M can
begin
Y
Y and Z are preceded by X
X
Z
Z
Y and Z can begin at the
same time, if you wish
Y
AA AA is preceded by X and Y
Z is preceded by X and Y
X
(B)
(D)
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A Simple Network (AON)
(cont’d)
A
14
C
3
Start
E
B
3
D
7
4
F
10
Finish
Calculate:
Critical Path
Project Duration
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The Critical Path
ES = 0
EF = 14
ES = 14
EF = 17
A
C
14
3
Start
ES = 17
EF = 21
E
B
3
ES = 0
EF = 3
D
7
ES = 3
EF = 10
= Critical Path
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4
ES = 21
EF = 31
F
10
Finish
ES = Early Start
EF = Early Finish
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Determining Slack
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How much slack is there
Where is it?
How do you know?
Why might you care?
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Determining Slack (cont’d)
ES = 0
EF = 14
LS = 0
LF = 14
A
14
ES = 14
EF = 17
LS = 14
LF = 17
C
3
Start
ES = 17
EF = 21
LS = 17
LF = 21
E
B
3
ES = 0
EF = 3
LS = 7
LF = 10
D
7
4
ES = 21
EF = 31
LS = 21
LF = 31
F
Work Back . . .
10
Finish
ES = Early Start
EF = Early Finish
LS = Late Start
LF = Late Finish
ES = 3
EF = 10
LS = 10
LF = 17
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Determining Slack (cont’d)
ES = 0
EF = 14
LS = 0
LF = 14
A
ES = 14
EF = 17
LS = 14
LF = 17
14
C
ES = 17
EF = 21
LS = 17
LF = 21
3
Start
E
B
3
ES = 0
EF = 3
LS = 7
LF = 10
D
7
ES = 3
EF = 10
LS = 10
LF = 17
What does all this mean?
4
ES = 21
EF = 31
LS = 21
LF = 31
F
10
Finish
Slack = LS - ES
CP = 0 Slack, where ES = LS
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Three Sequential Activities,
AON Format
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Activity Network, AON Format
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Activity Network, AOA Format
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Sample of Network
Construction, Figure 8-5
AON
AOA
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Sample of Network
Construction, Figure 8-6
AON
AOA
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Sample of Network
Construction, Figure 8-7
AON
AOA
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Networking Concurrent
Activities, Figure 8-8
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Activity c Not Required for e,
Figure 8-9
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Showing Precedents,
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Figure 8-10
8-38
MSP Gantt Chart, Figure 8-11
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MSP AON Network, Figure
8-12
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An AON Network for a 10Activity Project, Figure 8-13
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Distribution of Possible Activity
Times, Figure 8-14
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AON Network with Durations
and Variances, Figure 8-15
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AON Network with Earliest/Latest
Start/Finish Times, Figure 8-16
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Gantt Chart of Table 8-4,
Figure 8-17
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AON Network of Table 8-4,
Figure 8-18
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MSP Gantt Chart of Table 8-4,
Figure 8-19
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MSP Gantt Chart, Video Project,
Figure 8-20
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MSP AON Network, Video Project,
Figure 8-21
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MSP Calendar, Video Project,
Figure 8-22
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MSP Calendar, Video Project,
Figure 8-22 (continued)
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MSP Gantt Chart, Video Project,
Figure 8-23
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Probability Distribution,
Figure 8-24
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a, m, and b Estimates,
Figure 8-25
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Crystal Ball® Spreadsheet,
Figure 8-26
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CB Frequency Chart,
Figure 8-27
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CB Summary Statistics,
Figure 8-28
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CB Percentile Probabilities,
Figure 8-29
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CB Cumulative Probability Chart,
Figure 8-30
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Precedence Diagramming
Conventions, Figure 8-31
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Sample GERT Network,
Figure 8-33
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Apartment Complex Network,
Figure 8-35
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Hypothetical Network
3
13
1
30
16
2
5
20
5
6
6
TE=64
4
Calculate t(e) and Z for this network……
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Activity and Project Frequency Distributions
ACTIVITY
a
PROJECT
m
b
(A)
TE
(B)
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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!
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PERT Schedule Probability
Z = T(S) – T(E)
SSD(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
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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
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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
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[(b-a)/6]2
Var
Possible Project Durations
TS=67
TE=64
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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
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