ELC 347 project management

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

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

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

9. Early Start ID Number Early Finish Activity Float Activity Descriptor Late Start Activity Duration Late Finish Node Labels 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. Experience Historical data Research Modeling Experiments Breakdown/roll-up Delphi Method Panel of experts Consultants Three outside Estimates Ranging Other techniques Techniques for Estimating Duration

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. 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

21. Example

22. Special Case • If an activity has more than one processor its EPS is set to the latest EPF of all its processors

23. An example of forward pass

24. Backwards Pass • Use to calculate Slack • LS -> Latest start time • LF -> Latest finish time • TS -> total slack

25. An example of backward pass

26. Sketch the network described in the table. • Determine the ES, LS, EF, LF, and slack of each activity 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. A(3) B(6) C(9) A1(1) A2(1) A3(1) B1(2) B2(2) B3(2) C1(3) C2(3) C3(3) Laddering Activities Project ABC can be completed more efficiently if subtasks are used ABC=18 days Laddered ABC=12 days

29. 0 A 5 0 5 5 • B 15 • 5 10 15 15 C 18 15 3 18 0 Hammock 18 0 18 18 Hammock Activities Used as summaries for subsets of activities 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