1. Project Time Management
Part 2

2. Critical Path Method (CPM)
CPM is a network diagramming technique used to predict total project duration
A critical path for a project is the series of activities that determines the earliest time by which the project can be completed
The critical path is the longest path through the network diagram and has the least amount of slack or float
Slack or float is the amount of time an activity may be delayed without delaying a succeeding activity or the project finish date

3. Critical Path Method (CPM)
There are normally several tasks done in parallel on a project
Most projects have multiple paths on the network diagram
The longest path or the path containing the critical tasks is deriving the completion dates for a project
You are not finished with the project until you have completed all the tasks

4. Calculating the Critical Path
First develop a good network diagram, which in turn requires a good activity list based on the WBS.
Estimate the duration of each activity
Add the duration estimates for all activities on each path through the network diagram
The longest path is the critical path

5. Calculating the Critical Path (Cont’d)
What does critical path really mean?
The critical path shows the shortest time in which a project can be completed.
If one or more of the activities on the critical path takes longer than planned, the whole project schedule will slip unless the project manager takes corrective action

6. Determining the Critical Path for Project X

7. More on the Critical Path
A project team at Apple computer put a stuffed gorilla on the top of the cubicle of the person currently managing critical task
This would let others know that the person under the pressure don’t need to be disturbed or distracted.
The critical path is not the one with all the critical activities; it only accounts for time
There can be more than one critical path if the lengths of two or more paths are the same
In case of more than one critical path the project managers should keep track of all those critical paths
The critical path can change as the project progresses.

8. How Critical Paths Change,
Suppose activities A,B,C,D,E,F and G all start and finish as planned
Assume that activity I runs into problems and takes more than 4 days to complete
This would make path C,G,I,J be longer than other paths
Hence C,G,I,J would now be the Critical Path.

9. Using Critical Path Analysis to Make Schedule Trade-offs
It is important to know what the critical path is throughout the life of a project. So the project manager can make tradeoffs
Behind schedule tasks on the critical path need to be addressed by answering these questions
Should the schedule be renegotiated?
Should more resources be allocated on other items on the critical path to make up for lost time?
Is it ok if the project finishes behind schedule?
Project team can proactively manage schedule using the critical path analysis.

10. Using Critical Path Analysis to Make Schedule Trade-offs
Project Manager can use a technique to make tradeoffs. This technique involves determining the following
Free slack or free float is the amount of time an activity can be delayed without delaying the early start of any immediately following activities
Total slack or total float is the amount of time an activity may be delayed from its early start without delaying the planned project finish date
Early Start Date is the earliest possible time an activity can start based on the project network logic.

11. Using Critical Path Analysis to Make Schedule Trade-offs
Project Managers calculate free or total slack by conducting a forward pass or backward pass on the network diagram
A forward pass through the network diagram determines the early start and finish dates
A backward pass determines the late start and finish dates

12. Example of Forward Pass
Tasks D and E precedes task H
Early start date for task H would be early finish date of task E. As it’s greater than early finish date of task D

13. Calculating Early and Late Start and Finish Dates
B,C is critical path with no float or slack
Task A has 5 days of free and total float or slack

14. Free and Total Float or Slack for Project X

15. How to Find the Critical Path
General Foundry’s network with expected activity times
A 2
C 2
H 2
E 4
B 3
D 4
G 5
F 3
Start
Finish

16. How to Find the Critical Path
To find the critical path, need to determine the following quantities for each activity in the network
Earliest start time (ES): the earliest time an activity can begin without violation of immediate predecessor requirements
Earliest finish time (EF): the earliest time at which an activity can end
Latest start time (LS): the latest time an activity can begin without delaying the entire project
Latest finish time (LF): the latest time an activity can end without delaying the entire project

17. How to Find the Critical Path
In the nodes, the activity time and the early and late start and finish times are represented in the following manner
ACTIVITY t
ES EF
LS LF
Earliest times are computed as
Earliest finish time = Earliest start time + Expected activity time
EF = ES + t
Earliest start = Largest of the earliest finish times of immediate predecessors
ES = Largest EF of immediate predecessors

18. How to Find the Critical Path
At the start of the project we set the time to zero
Thus ES = 0 for both A and B
Start
A t = 2
ES = 0 EF = = 2
B t = 3
ES = 0 EF = = 3

19. How to Find the Critical Path
General Foundry’s ES and EF times
A 2
0 2
C 2
2 4
H 2
13 15
E 4
4 8
B 3
0 3
D 4
3 7
G 5
8 13
F 3
4 7
Start
Finish
Figure 13.4

20. How to Find the Critical Path
Latest times are computed as
Latest start time = Latest finish time – Expected activity time
LS = LF – t
Latest finish time = Smallest of latest start times for following activities
LF = Smallest LS of following activities
For activity H
LS = LF – t = 15 – 2 = 13 weeks

21. How to Find the Critical Path
General Foundry’s LS and LF times
A 2
0 2
C 2
2 4
H 2
13 15
E 4
4 8
B 3
0 3
1 4
D 4
3 7
G 5
8 13
F 3
4 7
10 13
Start
Finish
Figure 13.5

22. How to Find the Critical Path
Once ES, LS, EF, and LF have been determined, it is a simple matter to find the amount of slack time that each activity has
Slack = LS – ES, or Slack = LF – EF
From Table 13.3 we see activities A, C, E, G, and H have no slack time
These are called critical activities and they are said to be on the critical path
The total project completion time is 15 weeks
Industrial managers call this a boundary timetable

23. How to Find the Critical Path
General Foundry’s schedule and slack times
ACTIVITY
EARLIEST START, ES
EARLIEST FINISH, EF
LATEST START, LS
LATEST FINISH, LF
SLACK, LS – ES
ON CRITICAL PATH? A 2
Yes B 3 1 4 No C D 7 8 E F 10 13 6 G H 15
Table 13.3

24. How to Find the Critical Path
General Foundry’s critical path
A 2
0 2
C 2
2 4
H 2
13 15
E 4
4 8
B 3
0 3
1 4
D 4
3 7
G 5
8 13
F 3
4 7
10 13
Start
Finish
Figure 13.6

25. Using the Critical Path to Shorten a Project Schedule
Three main techniques for shortening schedules for activities on the critical path.
Shortening durations of critical activities/tasks by adding more resources or changing their scope
Crashing is a technique used to decrease the duration of the project by assigning additional resources to tasks and decreasing the duration required for those tasks. Main disadvantage?
Fast tracking activities by doing them in parallel or overlapping them. Main disadvantage?

26. Importance of Updating Critical Path Data
It is important to update project schedule information to meet time goals for a project
The critical path may change as you enter actual start and finish dates
If you know the project completion date will slip, negotiate with the project sponsor

27. Critical Chain Scheduling
A method of scheduling that considers limited resources when creating a project schedule and includes buffers to protect the project completion date
Uses the Theory of Constraints (TOC)
This theory says that at any given time the project has an aspect or constraint which limits its ability to achieve more of its goals.
For the system to attain any significant improvements the constraint might be identified and the whole system must be managed with it in mind

28. Critical Chain Scheduling
The important thing is availability of scarce resources like people, software or hardware.
Attempts to minimize multitasking
When a resource works on more than one task at a time
Multitasking can delay task completion
It can some times increase total duration like wasted setup time

29. Multitasking Example

30. Buffers and Critical Chain
A buffer is additional time to complete a task
Murphy’s Law states that if something can go wrong, it will, like fears about estimates being reduced from sponsor side.
Parkinson’s Law states that work expands to fill the time allowed
In traditional estimates, people often add a buffer to each task and use it if it’s needed or not
Critical chain scheduling removes buffers from individual tasks and instead creates:
Project buffers or additional time added before the project’s due date
Feeding buffers or additional time added before tasks on the critical path

31. Example of Critical Chain Scheduling

32. Program Evaluation and Review Technique (PERT)
PERT is a network analysis technique used to estimate project duration when there is a high degree of uncertainty about the individual activity duration estimates
PERT uses probabilistic time estimates
Duration estimates based on using optimistic, most likely, and pessimistic estimates of activity durations, or a three-point estimate
The main disadvantage is more work required than CPM

33. PERT Formula and Example
PERT weighted average =
optimistic time + 4X most likely time + pessimistic time 6
Example:
8 workdays + 4 X 10 workdays + 24 workdays = 12 days 6
where optimistic time = 8 days
most likely time = 10 days, and
pessimistic time = 24 days
Therefore, you’d use 12 days on the network diagram instead of 10 when using PERT for the above example

34. Schedule Control
The final process in project time management is schedule control
Like scope control the schedule control is a portion of integrated change control process under the project integration management
The goal of schedule control is to know the status of the schedule, influence the factors causing schedule changes, determine schedule changes and manage changes when they occur

35. Schedule Control Suggestions
Perform reality checks on schedules
Allow for contingencies
Don’t plan for everyone to work at 100% capacity all the time
Hold progress meetings with stakeholders and be clear and honest in communicating schedule issues

36. Controlling the Schedule
It is important to address conflicts and allow management insight if any thing gets out of hand
Project managers must use discipline to control schedule like setting firm dates for key milestones and emphasizing the need to follow them
Tools and techniques include:
Progress reports
A schedule change control system
Project management software, including schedule comparison charts like the tracking Gantt chart
Variance analysis, such as analyzing float or slack
Performance management, such as earned value (Chapter 7)

37. Reality Checks on Scheduling
First review the draft schedule or estimated completion date in the project charter
Prepare a more detailed schedule with the project team
Make sure the schedule is realistic and followed
Alert top management well in advance if there are schedule problems

38. Working with People Issues
Strong leadership helps projects succeed more than good PERT charts
Project managers should use:
Empowerment
Incentives
Discipline
Negotiation

39. Using Software to Assist in Time Management
Software for facilitating communications helps people exchange schedule-related information in the form of Network diagrams with critical paths information, Gantt charts etc
Decision support systems help analyze trade-offs that can be made
Project management software can help in various time management areas

40. Words of Caution on Using Project Management Software
Many people misuse project management software because they don’t understand important concepts behind creating a network diagram, evaluating critical path or setting a schedule baseline
You must enter dependencies to have dates adjust automatically and to determine the critical path
You must enter actual schedule information to compare planned and actual progress

41. Assignment # 1 Make a team of up to 3 people
Select a Software Project of your own choice
Develop Project Charter of the selected project
Deadline of this deliverable is