MIS 746 IS Project Management
Dr. Honghui Deng
Associate Professor
MIS Department
UNLV
3.1
Q&A
• What are the Three Constraints of
Project Management?
• What are the Time Killers for Project?
• Is time a resource for project
management?
3.2
Discussion
• Consider the idea that time is a
resource but also a constraint for IT
project management,
• Is this a contradiction?
3.3
Review of PERT/CPM
Video 5 PERT/CPM
3.4
PERT/CPM
PERT (Program Evaluation Review Technique)/
CPM (Critical Path Method) is a method of
scheduling tasks. It shows sequence by
detailed activities and time (hours, days,
weeks). It helps determine which task may
become a bottleneck and delay the entire
project. PERT is a planning and control tool
that helps accomplish project objectives on
time. It graphically illustrates the
interrelationships of events and activities
required to bring a project to its successful
conclusion.
3.5
A management tool
As a management tool, PERT helps the
analysts to
• Coordinate the various project tasks.
• See the relative importance of each activity.
• Determine the time to complete each
activity.
• Identify tasks that will delay the entire
project if they are not completed as
scheduled.
• Reschedule activities in order to reduce the
total time.
• Control project progress.
3.6
A network of activities
PERT is defined in terms of network. The network
consists of events and activities. All of the required
events are connected by arrows that indicate the
preceding and succeeding events. An event (A, B, C,
D, or E) is the beginning or ending of an activity. An
event can be considered as a milestone. Events have
no time dimension and usually are represented by a
circle. An activity (presented by an arrow) links two
successive events together and represents the work
required between these two events. An activity must
be accomplished before the following event can
occur. Let’s look at an example.
3.7
A simple example
Consider the list of four activities for
buying a software for your office:
Activity
A
B
C
D
Description
Identify needs and a vendor
Identify the source for funding
Develop a proposal for funding
Submit the proposal
Immediate
predecessors
B
A,C
The immediate predecessors for any activity are those
activities that, when completed, enable the start of that
activity.
3.8
Sequence of activities
• We can start work on activities A and B
anytime, since neither of these activities
depends upon the completion of prior
activities.
• C activity cannot start until activity B
has been completed, and activity D
cannot start until both activities A and C
have been completed.
• The graphical representation (next slide)
is referred to as the PERT/CPM network
for project.
3.9
Network of four activities
Arrows indicate project activities
A
1
3
D
4
C
B
2
Nodes indicate start and finish of activities
3.10
Another example
Develop the network for a project with
following activities and immediate
predecessors:
Activity
A
B
C
D
E
F
G
Immediate
predecessors
B
A, C
C
C
D,E,F
First, attempt for the first five (A,B,C,D,E) activities
3.11
Network of first five activities
A
1
4
E
B
C
2
3.12
D
3
5
We need to introduce a
dummy activity
Network of seven activities
A
1
3
D
4
G
7
E
B
C
2
5
F
6
•Note how the network correctly identifies D, E, and F as the
immediate predecessors for activity G.
•Dummy activities can be used to identify precedence
relationships correctly as well as to eliminate the possible
confusion of two or more activities having the same starting
and ending nodes.
3.13
Scheduling with activity time
Activity
A
B
C
D
E
F
G
H
I
Immediate
predecessors
A
A
A
E
D,F
B,C
G,H
Completion
Time (week)
5
6
4
3
1
4
14
12
2
Total ……
51
This information indicates that the total time required to
complete activities is 51 weeks. However, we can see from
the network that several of the activities can be carried out
simultaneously (A and B, for example).
3.14
Network with activity time
D
3
2
5
E
1
A
5
C
F
4
4
4
1
G
14
6
B
6
I
2
7
H
12
3
Each activity letter is written above and
each activity time is written bellow the arc
To complete the total project completion time we will have to
analyze the network and identify what is called critical path.
A path is a sequence of connected activities that leads from the
starting node (1) to the completion node (7).
3.15
Earliest start & earliest finish time
• We are interested in the longest path through
the network, i.e., the critical path.
• Starting at the network’s origin (node 1) and
using a starting time of 0, we compute an
earliest start (ES) and earliest finish (EF) time for
each activity in the network.
• The expression EF = ES + t can be used to
find the earliest finish time for a given activity.
For example, for activity A, ES = 0 and t = 5;
thus the earliest finish time for activity A is
EF = 0 + 5 = 5
3.16
Arc with ES & EF time
ES = earliest finish time
ES = earliest start time
Activity
2
1
t = expected activity time
3.17
Network with ES & EF time
D[5,8]
3
2
5
7
4
1
6
3
Earliest start time rule: The earliest start time for an activity
leaving a particular node is equal to the largest of the
earliest finish times for all activities entering the node.
3.18
Latest start & latest finish time
• To find the critical path we need a backward
pass calculation.
• Starting at the completion point (node 7) and
using a latest finish time (LF) of 26 for activity I,
we trace back through the network computing
a latest start (LS) and latest finish time for each
activity.
• The expression LS = LF – t can be used to
calculate latest start time for each activity. For
example, for activity I, LF = 26 and t = 2, thus
the latest start time for activity I is
LS = 26 – 2 = 24
3.19
Network with LS & LF time
D[5,8]
3[7,10]
2
5
7
4
1
6
3
Latest finish time rule: The latest finish time for an activity
entering a particular node is equal to the smallest of the latest
start times for all activities leaving the node.
3.20
Activity, duration, ES, EF, LS, LF
EF = earliest finish time
ES = earliest start time
Activity
3
2
LF = latest finish time
LS = latest start time
3.21
Slack or free time
Slack = LS – ES = LF – EF
Slack is the length of time an activity can be
delayed without affecting the completion date
for the entire project. For example,
slack for C = LS – ES = 8 – 5 = 3 weeks
or
LF – EF = 12 – 9 = 3 weeks.
This means activity C can be delayed up to 3
weeks (start anywhere between weeks 5 and
8).
3.22
Activity schedule for our example
Activity
A
B
C
D
E
F
G
H
I
3.23
Earliest
start (ES)
Latest
start (LS)
0
0
5
5
5
6
10
9
24
0
6
8
7
5
6
10
12
24
Earliest
finish
(EF)
5
6
9
8
6
10
24
21
26
Latest
finish
(LF)
5
12
12
10
6
10
24
24
26
Slack
(LS-ES)
0
6
3
2
0
0
0
3
0
Critical
path
Yes
Yes
Yes
Yes
Yes
Important questions
• What is the total time to complete the project?
– 26 weeks if all individual activities are completed
on schedule.
• What are the scheduled start and completion
times for each activity?
– ES, EF, LS, LF are given for each activity.
• What activities are critical and must be
completed as scheduled in order to keep the
project on time?
– Critical path activities: A, E, F, G, and I.
• How long can non-critical activities be delayed
before they cause a delay in the project’s
completion time
3.24
– Slack time available for all activities are given.