9-1 elc 347 project management week 10. 9-2 agenda integrative project –2nd part graded a few...
TRANSCRIPT
9-1
ELC 347 project management
Week 10
9-2
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
9-3
Project Scheduling: Networks, Duration Estimation,
and Critical PathChapter 9
© 2007 Pearson Education
9-4
9-5
9-6
Project Scheduling Terms
• Successors
• Predecessors
• Network diagram
• Serial activities
• Concurrent activities
ED
C
B
A F
• Merge activities
• Burst activities
• Node
• Path
• Critical Path
9-7
Network Diagrams
Show interdependence
Facilitate communication
Help schedule resources
Identify critical
activities
Determine project completion
Show start & finish dates
9-8
AOA Vs. AON
The same mini-project is shown with activities on arc…
C
ED
B F
E
C
DB F
…and activities on node.
9-9
Node LabelsEarly Start
Activity Float Activity Descriptor
Late Start
ID Number
Activity Duration
Late Finish
Early Finish
Basic mathES + DUR = EFLS + DUR = LF
ES+AF=LS
9-10
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
9-11
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
9-12
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
9-13
9-14
Duration Estimation Methods
• Past experience• Expert opinion• Mathematical derivation – Beta distribution
– Most likely (m)– Most pessimistic (b)– Most optimistic (a)
22 =
6
b aActivity Variance
4 = TE
6
a m bActivity Duration
9-15
Task Predecessor a m b
Z -- 7 8 15
Y Z 13 16 19
X Z 14 18 22
W Y, X 12 14 16
V W 1 4 13
T W 6 10 14
S T, V 11 14 19
1. Sketch the network described in the table.
2. Determine the expected duration and variance of each activity.
Duration estimate.xls
9-16
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
9-17
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
9-18
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
9-19
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
9-20
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
9-21
Example
3 4 7
A
7 5 12
B
9-22
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
A7 5 12
C0 5 5
B
9-23
An example of forward pass
0 0 0
Start
8 4 12
F
0 4 4
D
4 8 12
C
25
4 29
Finish
0 5 5
A
16
5 21
I
21
4 25
J
4 4 8
E
16
7 23
H
12
4 16
G
5 4 9
B
9-24
Backwards Pass
• Use to calculate Slack– LS -> Latest start time– LF -> Latest finish time– TS -> total slack
ES DUR EF
ActivityLS TS LF
9-25
An example of backward pass
0 0 0
Start
0 0 0
8 4 12
F
12
4 16
0 4 4
D
0 0 4
4 8 12
C
4 0 12
25
4 29
Finish
25
0 29
0 5 5
A
3 3 8
16
5 21
I
16
0 21
21
4 25
J
21
0 25
4 4 8
E
8 4 12
16
7 23
H
18
2 25
12
4 16
G
12 0 16
5 4 9
B
8 3 12
9-26
Task Predecessor Time
A -- 4
B A 9
C A 11
D B 5
E B 3
F C 7
G D, F 3
H E, G 2
K H 1
1. Sketch the network described in the table.
2. Determine the ES, LS, EF, LF, and slack of each activity
SLACK.xls
9-27
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
9-28
Laddering Activities
Project ABC can be completed more efficiently if subtasks are used
A(3) B(6) C(9) ABC=18 days
Laddered ABC=12 days
A1(1) A2(1) A3(1)
B1(2) B2(2) B3(2)
C1(3) C2(3) C3(3)
9-29
Hammock Activities
Used as summaries for subsets of activities
0 A 5
0 5 5
5 B15
5 1015
15 C 18
15 3 18
0 Hammock 18
0 18 18
Useful with a complex project or one that has
a shared budget
9-30
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