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

2. Overview
WBS to Schedule Process
PERT
Schedule Types
CPM

3. Scheduling
Def.: A schedule is the conversion of a project action plan into an operating timetable
Is 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 (routine) 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 Networks
Such networks are a powerful tool for planning and controlling a project and have the following benefits:
consistent framework for planning, scheduling, monitoring, and controlling the project
illustrates the interdependence of all tasks, work packages, and work elements
denotes the times when specific resources are or must be available for work on a given task

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

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

9. Gantt Charts Advantages: easily understood / constructed / maintained
Great visual tool to know project status (early, on time, late)
requires frequent updating, but are easy to maintain
Most popular way of providing a clear picture of the current state of a project (client, management, etc.)

10. Gantt Charts Disadvantages: superficial
Hard to see activity precedents at times.

11. Gantt Charts
Show planned and actual progress for a number of tasks displayed against a horizontal time scale
Effective and easy-to-read method of indicating the actual current status for each set of tasks compared to planned progress for each item
Helpful in expediting, sequencing, and reallocating resources among tasks
Usually do not show technical dependencies

12. Simple Schedule – Gantt Chart

13. Network Techniques: PERT and CPM
With the exception of Gantt charts, 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.

14. Network Techniques: PERT and CPM
Advantages
Can visualize task relationships.
Facilitates CP (Critical Path) Calculation
Can see impact of decisions on downstream activities.
Disadvantages
May be complex, not easy to understand at a glance.

15. New Names for PERT and CPM
Most everyone knows techniques as PERT and CPM.
In 2005, PMI decided to rename them.
New names:
ADM/PERT: Arrow Diagram Method
PDM/CPM: Precedence Diagram Method.

16. 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

17. 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

18. 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

19. 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

20. Sample Input Information to a CPM Problem (Action Plan)
Activity* A B C D E F
Duration (weeks) 14 3 7 4 10
Predecessor
Start
A,B
C,D
* Activities could be Deliverables, Tasks, Subtasks or Operations.

21. (AON): Letters indicate activities, Arrows indicate relations
A Sample Network (AON)
Start A 14 C 3 E 4 F 10 B D 7
Finish
Calculate:
Project Duration
Critical Path (CP)
Activities on CP
(AON): Letters indicate activities, Arrows indicate relations

22. The Critical Path (CP) A 14 C 3 Start E 4 F 10 B 3 D 7 Finish ES = 0
ES: Earliest (Possible) Starting Time
EF: Earliest (Possible Finish Time

23. Determining Slack
How much slack is there
Where is it?
How do you know?
Why might you care?

24. Determining Slack Work Back . . . Critical Activity
Start A 14 C 3 E 4 F 10 B D 7
Finish
ES = 0
EF = 14
LS = 0
LF = 14
ES = 14
EF = 17
LS = 14
LF = 17
ES = 17
EF = 21
LS = 17
LF = 21
ES = 21
EF = 31
LS = 21
LF = 31
EF = 3
LS = 7
LF = 10
ES = 3
EF = 10
LS = 10
Work Back . . .
Critical Activity
LS: Latest Starting Time
LF: Latest Finish Time

25. PERT

26. AOA (Activity on Arrow) Network Building Blocks80 79
Install software
Event
Activity

27. AOA (Activity on Arrow) Network Building Blocks
AON
AOA

28. AOA (Activity on Arrow) Network Building Blocks
AON
AOA
Activity on Node
Activity on Arrow

29. AOA (Activity on Arrow) Network Building Blocks
Any activity must have its source in one and only one node. If two activities occur between the same two nodes, insert a “dummy node” & activity w/duration 0.

30. AOA (Activity on Arrow) Network Building Blocks
If c is not required to start e, then separate c by using another dummy node and arrow: a and b are required to start e, and a,b and c are required for d.

31. AOA (Activity on Arrow) Network Building Blocks
- a precedes d; a and b precedes e; b and c precedes f; a does not precede f.

32. Gantt Chart

33. Gantt Chart

34. PERT

35. PERT Activity Calculation
TE = 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!

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

37. Distribution of Possible Activity Times
What is the probability of finishing the project (or an activity) in x days?

38. Probability Distribution
Probability of finishing the project in 50 days? About 89%
This is a tool to set your confidence in completing in X days.

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

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

41. Variance of Activity Estimatesb
t(e)
[(b-a)/6]2
Var
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

42. Possible Project Durations
TE=64
TS=67

43. 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

44. Z-Table Expanded

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