ELC 347

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ELC 347

• DAY 8

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Agenda

• Questions
• Assignment 3 Corrected
• 4 As , One non-submit
• Assignment 4 Due
• Capstone Proposal Due
• Group Progress report due
• Exam 2
• Slight Change
• 10 M/C (5 points each) 5 essays (10 points each)
• 1 hour 15 minutes
• Open book, Open Notes
• Ghattas 4-8, Project 8-10
• Group Project Meeting (30 Min)
• Discussion on Network Analysis and Duration
  Estimating

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Network Analysis and Duration Estimating

• Laying the Groundwork for Commitment
• Setting Duration Estimates
• Determining the critical Path
• Meeting external deadlines

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Groundwork for commitment

• Ask the people that actually doing the work
• If more than one is capable ask the one with the
  most experience
• Be realistic
• Be an advocate for your team

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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

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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

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Special Cases (Out of your hands)

• Inspections
• Deliveries
• Breakdowns and repairs
• Approvals

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Normalizing Duration

• Goal is most cost-efficient plan
• Determine the most cost-efficient technical
  approach
• Make and estimate of long the most cost efficient
  method will take to complete
• Selectively adjust you estimate for any activity
  that is subject to common problems.

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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

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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

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Whats the Critical Path

• The longest path based on precedence of
  activities and durations through a PERT/CPM
  network
• Its 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

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Finding the critical path

• Use forward pass Calculations
• Each activity should have
• EPS ?earliest possible Start time
• EPF ? earliest possible finish time
• DUR ? duration
• EPF EPS DUR

EPS DUR EPF
Activity Activity Activity

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Example
3 4 7
A A A

7 5 12
B B B

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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 A A

7 5 12
C C C

0 5 5
B B B

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An example of forward pass
16 7 23
H H H

12 4 4 16 16
G G G G G

5 4 9
B B B

0 5 5
A A A

25 4 29
Finish Finish Finish

4 8 12
C C C

16 5 21
I I I

0 0 0
Start Start Start

8 4 12
F F F

21 4 25
J J J

0 4 4
D D D

4 4 8
E E E

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Backwards Pass

• Use to calculate Slack
• LAS -gt Latest start time
• LAF -gt Latest finish time
• TS -gt total slack

EPS DUR EPF
Activity Activity Activity
LAS TS LAF
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An example of backward pass
16 7 23
H H H
18 2 25
12 4 4 16 16
G G G G G
12 12 0 0 16
5 4 9
B B B
8 3 12
0 5 5
A A A
3 3 8
25 4 29
Finish Finish Finish
25 0 29
4 8 12
C C C
4 0 12
16 5 21
I I I
16 0 21
0 0 0
Start Start Start
0 0 0
8 4 12
F F F
12 4 16
21 4 25
J J J
21 0 25
0 4 4
D D D
0 0 4
4 4 8
E E E
8 4 12
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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

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Optimizing the plan

• Would bringing more expert talent to bear on the
  project speed it up?
• Are there changes we could make in the resource
  procurement process to shorten wait times?
• Would round the clock scheduling shorten
  duration?
• Would more money motivate the team to work
  faster?
• Would an organizational change speed things up?
• Do we think it will take this long just because
  it always has, or are there other ways to so
  this, which we havent thought of yet, that would
  shrink the timetable?

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3 Lines of defense

• Relieve the critical path
• Sharpen your pencil
• Crash activities

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Summary

• Construct a CPM
• Estimate normal durations
• Do a forward pass
• Identify Critical Path
• Optional
• Do a backward pass to identify slack times
• Conduct a reality check
• Optimize the plan
• 1st line of defense - relieve the critical path
• 2nd line of defense - sharpen your pencil
• 3rd line of defense - crash activities