1. Project Management: A Managerial Approach
Chapter 8 – Scheduling

2. Overview
WBS to Schedule Process
PERT
Schedule Types
CPM

3. 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

4. Scheduling
In a project environment, the scheduling function is more important than it would be in an ongoing operation
Projects lack the continuity of day-to-day operations and often present much more complex problems of coordination

5. Scheduling
The basic approach of all scheduling techniques is to form a network of activity and event relationships
This network should graphically portray the sequential relations between the tasks in a project
Tasks that must precede or follow other tasks are then clearly identified, in time as well as function

6. Scheduling
Such networks are a powerful tool for planning and controlling a project and have the following benefits:
It is a consistent framework for planning, scheduling, monitoring, and controlling the project
It illustrates the interdependence of all tasks, work packages, and work elements
It denotes the times when specific individuals must be available for work on a given task

7. Scheduling Network benefits (cont.):
It aids in ensuring that the proper communications take place between departments and functions
It determines an expected project completion date
It identifies so-called critical activities that, if delayed, will delay the project completion time
It identifies activities with slack that can be delayed for specific periods without penalty

8. Scheduling Network benefits (cont.):
It determines the dates on which tasks may be started - or must be started if the project is to stay on schedule
It illustrates which tasks must be coordinated to avoid resource timing conflicts
It illustrates which tasks may run, or must be run, in parallel to achieve the predetermined project completion date
It relieves some interpersonal conflict by clearly showing task dependencies

9. Simple Schedule – Gantt Chart

10. 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

11. Network Techniques: PERT and CPM
PERT has been primarily used for research and development projects
CPM was designed for construction projects and has been generally embraced by the construction industry
The two methods are quite similar and are often combined for educational presentation

12. 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

13. 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

14. 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

15. Hypothetical Network 2 5 6 1 4 3 16 20 13 30
TE=64
Calculate t(e) and Z for this network……

16. Activity and Project Frequency Distributionsm b TE
(A)
(B)

17. PERT Activity Calculation
t(e) = a + 4m + b a = Most Optimistic (MO)
6 m = Most Likely (ML)
b = Most Pessimistic (MP)
t(e) = Activity Duration
When a single estimate for activity time is not sufficient!

18. PERT Schedule Probability
Z = T(S) – T(E) Z = Probability of
√SSD(T[E]) Meeting Schedule
Z = T(S) – T(E) T(S) = Scheduled Duration
√ΣVar(T[E])
T(E) = Critical Path Duration
Z is derived from a table of predetermined probabilities

19. PERT Activity Times & Variancesb
t(e)
1-2 17 29 47 30
2-3 6 12 24 13
2-4 16 19 28 20
3-5
4-5 2 5 14
5-6 8

20. Variance of Activity Estimatesb
t(e)
[(b-a)/6]2
Var
1-2 17 29 47 30 25
2-3 6 12 24 13 9
2-4 16 19 28 20 4
3-5 1
4-5 2 5 14
5-6 8

21. Critical Path 6 20 13 5 16 30 2 3 4 1
TE = = 64
Var(TE) = = 36

22. Possible Project Durations
TE=64
TS=67
Z = (67 – 64) / √( ) = 0.5
Hence, the probability of meeting the target schedule (Ts) is 0.69 (69%)

23. Z Table 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

24. Z-Table Expanded

25. 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

26. Gantt Charts There are several advantages to the use of Gantt charts:
Even though they may contain a great deal of information, they are easily understood
While they may require frequent updating, they are easy to maintain
Gantt charts provide a clear picture of the current state of a project
They are easy to construct

27. 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

28. Drawing Networks

29. Hypothetical Network 3 1 2 5 6 4

30. AOA Network Building Blocks80 79
Install software
Event
Activity

31. Partial Koll Business Center - AOA4 5 1 3 2
A Application approval
D Service availability check
C Traffic study
B Construction plans

32. Partial AOA Network 2 3 1 4 A X C B E
(A)
(B)
(C)

33. Partial AOA Network 2 3 1 4 A B C X E (D) 5 D 2 3 1 4 A B C X E (E) 5F ?

34. KOLL BUSINESS CENTER County Engineers Design Department
Full AOA Network 2 3 1 4
A 5 B
C 10 X 5 15 6 7 8 Y
F 10
G 170
H 35
E 15
D 5
Legend
KOLL BUSINESS CENTER County Engineers Design Department
Activity Duration

35. Activity-on-Node Network FundamentalsX Y Z
Y and Z are preceded by X
Y and Z can begin at the
same time, if you wish
(B) A B C
A is preceded by nothing B is preceded by A C is preceded by B
(A) J K L M
J, K, & L can all begin at the same time, if you wish (they need not occur simultaneously)
All (J, K, L) must be completed before M can begin
but AA
(C)
(D)
Z is preceded by X and Y
AA is preceded by X and Y