ELC 347

DAY 8

Agenda

Questions Assignment 3 Corrected

4 A’s , 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

Network Analysis and Duration Estimating

Laying the Groundwork for Commitment

Setting Duration Estimates Determining the critical Path Meeting external deadlines

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

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

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

Special Cases (Out of your hands)

Inspections Deliveries Breakdowns and repairs Approvals

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.

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

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

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

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

Example

3 4 7

A

7 5 12

B

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

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

Backwards Pass

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

EPS DUR EPF

ActivityLAS TS LAF

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

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

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 haven’t thought of yet, that would shrink the timetable?

3 Lines of defense

Relieve the critical path Sharpen your pencil Crash activities

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