1. ELC 347 project management
Week 10

2. Agenda Integrative Project
2nd part Graded
A few Minor problems
3nd part Due
Outline of deliverables (posted in WebCT)
Quiz 2 is postedand must be completed by Nov 9
Chapters 5-9, 20 short essays (4 from each chapter)
Take home exam with 48 hours time limit
Three will only be 3 Quizzes instead of the 4 mentioned in the syllabus
Password is “CreepyScope”
Today we will discuss Project Scheduling

3. Project Scheduling: Networks, Duration Estimation, and Critical Path
Chapter 9
© 2007 Pearson Education

6. Project Scheduling Terms
Successors
Predecessors
Network diagram
Serial activities
Concurrent activities
Merge activities
Burst activities
Node
Path
Critical Path E D C B A F

7. Network Diagrams Help schedule resources Show interdependence
Show start & finish dates
Facilitate communication
Determine project completion
Identify critical activities

8. AOA Vs. AON The same mini-project is shown with activities on arc…D B F
…and activities on node. E D B F C

9. Node Labels Basic math ES + DUR = EF LS + DUR = LF ES+AF=LS
Early Start
Activity Float
Activity Descriptor
Late Start
ID Number
Activity Duration
Late Finish
Early Finish
Basic math
ES + DUR = EF
LS + DUR = LF
ES+AF=LS

10. CPM versus PERT PERT was developed by US Navy in the 1950s’
CPM was developed by Remington Rand and DuPont around the same time.
Only difference is in durations estimating
Pert uses 3 cases Most optimistic, most pessimistic and most likely and determines probability for each
DoPo + DpOp +DePe = final duration
CPM use only the most likely duration

11. Duration Estimating
Duration – the elapsed time from the start of an activity until it is finished
Effort -- the actual time spent on the project
Example
Tony work on a project task for 20 hours at 4 hours per day starting Monday mourning. The project task was completed Late Friday
Effort – 20 hours
Duration – 5 days

12. Techniques for Estimating Duration
Experience
Historical data
Research
Modeling
Experiments
Breakdown/roll-up
Delphi Method
Panel of experts
Consultants
Three outside Estimates
Ranging
Other techniques

14. Duration Estimation Methods
Past experience
Expert opinion
Mathematical derivation – Beta distribution
Most likely (m)
Most pessimistic (b)
Most optimistic (a)

15. Sketch the network described in the table.
Determine the expected duration and variance of each activity.
Task
Predecessor a m b Z -- 7 8 15 Y 13 16 19 X 14 18 22 W
Y, X 12 V 1 4 T 6 10 S
T, V 11
Task a b c Mean Variance Z Y X W V T S
Task Early Start Early Finish Late Start Late Finish Slack Z Y X W V T S
Project Length 64
Project Variance
Project Std.dev
Duration estimate.xls

16. Constructing the Critical Path
Forward pass – an additive move through the network from start to finish
Determines ES and EF using ES+DUR = EF
If 2 (or more) EF from proceeding uses largest
Backward pass – a subtractive move through the network from finish to start
Determines LS and LF using LF- DUR = LS
If 2 (or more) LS from succeeding use smallest
Determine AF using LS-ES = AF
Critical path – the longest path from end to end which determines the shortest project length

17. Rules for Forward/Backward Pass
Forward Pass Rules (ES & EF)
ES + Duration = EF
EF of predecessor = ES of successor
Largest preceding EF at a merge point becomes EF for successor
Backward Pass Rules (LS & LF)
LF – Duration = LS
LS of successor = LF of predecessor
Smallest succeeding LS at a burst point becomes LF for predecessor

18. Calculating a Project Duration
Determine each activity and its predecessors
Determine an estimated duration for each activity
Find the “Critical Path”
Add up the durations along the critical path

19. Whats the “Critical Path”
The longest path based on precedence of activities and durations through a PERT/CPM network
It’s critical because
Its combined length determines the length of the project
It has NO slack
Delay of any activities on the critical path delays the entire project

20. Finding the critical path
Use “forward pass” Calculations
Each activity should have
ES earliest possible Start time
EF  earliest possible finish time
DUR  duration
EF = ES + DUR ES
DUR EF
Activity

21. Example 3 4 7 A 7 5 12 B

22. Special Case
If an activity has more than one processor its EPS is set to the latest EPF of all its processors 3 4 7 A 7 5 12 C 5 B

23. An example of forward pass5 4 9 B 12 4 16 G 16 7 23 H 5 A 25 4 29
Finish 4 8 12 C 16 5 21 I
Start 8 4 12 F 21 4 25 J 4 D 4 8 E

24. Backwards Pass Use to calculate Slack LS -> Latest start time
LF -> Latest finish time
TS -> total slack ES
DUR EF
Activity LS TS LF

25. An example of backward pass12 4 16 G 16 7 23 H 18 2 25 5 4 9 B 8 3 12 5 A 3 8 25 4 29
Finish 4 8 12 C 16 5 21 I
Start 8 4 12 F 16 21 4 25 J 4 D 4 8 E 12

26. Sketch the network described in the table.
Task
Predecessor
Time A -- 4 B 9 C 11 D 5 E 3 F 7 G
D, F H
E, G 2 K 1
Sketch the network described in the table.
Determine the ES, LS, EF, LF, and slack of each activity
Task ES EF LS LF Slack A B C D E F G H K
SLACK.xls

27. Examine Critical Path for Reality Check
Is the total duration typical?
Are the durations of the CP activities typical?
Reexamine all CP activity durations
Reexamine assumptions

28. Laddering Activities
Project ABC can be completed more efficiently if subtasks are used
ABC=18 days
A(3)
B(6)
C(9)
A1(1)
A2(1)
A3(1)
B1(2)
B2(2)
B3(2)
C1(3)
C2(3)
C3(3)
Laddered ABC=12 days

29. Useful with a complex project or one that has a shared budget
Hammock Activities
Used as summaries for subsets of activities
0 A 5
B 15
15 C 18
0 Hammock 18
Useful with a complex project or one that has a shared budget

30. Reducing the Critical Path
Eliminate tasks on the CP
Convert serial paths to parallel when possible
Overlap sequential tasks
Shorten the duration on critical path tasks
Shorten
early tasks
longest tasks
easiest tasks
tasks that cost the least to speed up