Lecture
3
Project Scheduling
CP - Chapter 10
1
Project Management

How is it different?

Limited time frame
 Narrow focus, specific objectives

Why is it used?

Special needs
 Pressures for new or improves products or services

Definition of a project

2
Unique, one-time sequence of activities designed
to accomplish a specific set of objectives in a
limited time frame
Project Management

What are the Key Metrics

Time
 Cost
 Performance objectives

What are the Key Success Factors?

Top-down commitment
 Having a capable project manager
 Having time to plan
 Careful tracking and control
 Good communications
3
Project Management

What are the tools?

Work breakdown structure
 Network diagram
 Gantt charts
 Risk management
4
Project Manager
Responsible for:
Work
Human Resources
Communications
5
Quality
Time
Costs
Key Decisions
6

Deciding which projects to implement

Selecting a project manager

Selecting a project team

Planning and designing the project

Managing and controlling project resources

Deciding if and when a project should be
terminated
Ethical Issues
7

Temptation to understate costs

Withhold information

Misleading status reports

Falsifying records

Compromising workers’ safety

Approving substandard work

http://www.pmi.org/
PERT and CPM
PERT: Program Evaluation and Review Technique
CPM: Critical Path Method





Graphically displays project activities
Estimates how long the project will take
Indicates most critical activities
Show where delays will not affect project
PERT and CPM have been used to plan, schedule, and control
a wide variety of projects:




8
R&D of new products and processes
Construction of buildings and highways
Maintenance of large and complex equipment
Design and installation of new systems
PERT/CPM

PERT/CPM

used to plan the scheduling of individual
activities that make up a project.

Projects may have as many as several
thousand activities.
 Complicating factor in carrying out the
activities

9
some activities depend on the completion of
other activities before they can be started.
PERT/CPM

Project managers rely on PERT/CPM to help
them answer questions such as:

What is the total time to complete the project?
 What are the scheduled start and finish dates for
each specific activity?
 Which activities are critical?


How long can non-critical activities be delayed

10
must be completed exactly as scheduled to keep
the project on schedule?
before they cause an increase in the project
completion time?
Planning and Scheduling
Activity
Locate new
facilities
Interview staff
Hire and train staff
Select and order
furniture
Remodel and install
phones
Furniture setup
Move in/startup
11
0
2
4
6
8
10 12
14
16
18
20
Project Network

Project network

constructed to model the precedence of the
activities.
 Nodes represent activities
 Arcs represent precedence relationships of the
activities

Critical path for the network

12
a path consisting of activities with zero slack
Project Network – An Example
8 weeks
Locate
facilities
A
6 weeks
Order
furniture
B
F
11 weeks
Remodel
E
S
4 weeks
Interview
C
13
3 weeks
Furniture
setup
9 weeks
Hire and
train
D
G
Move
in
1 week
Management Scientist Solution
Critical Path
Path
Length
Slack
(weeks)
A-B-F-G
A-E-G
C-D-G
14
18
20
14
2
0
6
Uncertain Activity Times

Three-time estimate approach


the time to complete an activity assumed to
follow a Beta distribution
An activity’s mean completion time is:
t = (a + 4m + b)/6




15
a = the optimistic completion time estimate
b = the pessimistic completion time estimate
m = the most likely completion time estimate
An activity’s completion time variance is
2 = ((b-a)/6)2
Uncertain Activity Times

In the three-time estimate approach, the critical
path is determined as if the mean times for the
activities were fixed times.
 The overall project completion time is assumed to
have a normal distribution

with mean equal to the sum of the means along the
critical path, and
 variance equal to the sum of the variances along the
critical path.
16
Example
Immediate
Activity Predecessor
17
Optimistic
Time (a)
Most Likely
Time (m)
Pessimistic
Time (b)
A
--
4
6
8
B
--
1
4.5
5
C
A
3
3
3
D
A
4
5
6
E
A
0.5
1
1.5
F
B,C
3
4
5
G
B,C
1
1.5
5
H
E,F
5
6
7
I
E,F
2
5
8
J
D,H
2.5
2.75
4.5
K
G,I
3
5
7
Management Scientist Solution
18
Key Terminology

Network activities

ES: early start
 EF: early finish
 LS: late start
 LF: late finish

Used to determine

Expected project duration
 Slack time
 Critical path
19
The Network Diagram (cont’d)

Path



Critical path


Activities on the critical path
Slack

20
The longest path; determines expected project duration
Critical activities


Sequence of activities that leads from the starting node
to the finishing node
AON path: S-1-2-6-7
Allowable slippage for path; the difference the length
of path and the length of critical path
Computing Algorithm

Network activities

ES: early start
 EF: early finish
 LS: late start
 LF: late finish

Used to determine

Expected project duration
 Slack time
 Critical path
21
Advantages of PERT

Forces managers to organize

Provides graphic display of activities

Identifies

Critical activities

Slack activities
4
2
1
5
3
22
6
Limitations of PERT
23

Important activities may be omitted

Precedence relationships may not be correct

Estimates may include a fudge factor

May focus solely on critical path