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Probabilistic Activity Time
This document discusses probabilistic activity times in project management. It explains that probabilistic estimates allow for variation by using three time estimates - optimistic, most likely, and pessimistic - for each activity. These estimates are used to model the activity times with a beta distribution defined by a mean and variance. An example project network is presented that calculates earliest and latest times, slack, and performs probabilistic analysis to determine the likelihood of completing within a proposed time.
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Probabilistic Activity Time
- 1. Probabilistic Activity Times ProbabilisticTime Estimates Carrine Kezia Aulia :: 102183022
- 2. • Single timeestimates • Didn’t allow for any variation • AT treated as if they are known for certain COMPARISON CPM AND PERTREVIEW • Multiple time estimates • Allow for any variation • AT treated as probabilistic PERT uses probabilistic activity times CPM PERT
- 3. Approach to estimatingactivity times WHAT IS PROBABILISTIC ACTIVITY TIMES?What’s it all about? • Completion time estimates can be estimated using the Three Time EstimateThree Time Estimate approachapproach • In this approach, three time estimates are required for each activity
- 4. MOST LIKELY TIME(m) THREE TIME ESTIMATES OPTIMISTIC TIME (a) PESSIMISTIC TIME (b) 1 2 3 most frequently occur if the activity were repeated many times the shortest possible time to complete the activity if everything went right the longest possible time to complete the activity if everything went wrong
- 5. with THREE TIMEestimates, the activity completion time can be approximated by a BETA DISTRIBUTION BETA DISTRIBUTION BETA DISTRIBUTIONS CAN COME IN A VARIETY OF SHAPES :
- 6. FORMULA MEAN AND VARIANCE a+ 4m + b 6 b - a 6 2 mean (expected time) variance σ2 t MOST LIKELY TIME (m) OPTIMISTIC TIME (a) PESSIMISTIC TIME (b)
- 7. EXAMPLEA PROJECT NETWORKWITH PROBABILISTIC TIME ESTIMATE
- 8. EXAMPLEACTIVITY TIME ESTIMATES a+ 4m + b 6 b - a 6 2 t σ2
- 9. EXAMPLEACTIVITY EARLIEST ANDLATEST TIMES AND SLACK
- 10. EXAMPLEACTIVITY EARLIEST ANDLATEST TIMES AND SLACK 0 8 8 8 5 13 0 6 6 3 0 3 3 6 9 4 3 7 2 3 5 7 9 16 4 9 13 4 13 17 9 16 25 2516 2521 2116 169 1612 1614 95 52 9660 91 EXPECTED TIME : 25 CRITICAL PATH : 2-5-8-11
- 11. EXAMPLEACTIVITY EARLIEST ANDLATEST TIMES AND SLACK 25 WEEKS 6,89 WEEKS
- 12. EXAMPLEPROBABILISTIC ANALYSIS OFTHE PROJECT NETWORK ADD ALL THE σ2 OFF THE CRITICAL PATH S D what does this formula means? what does these numbers mean?
- 13. EXAMPLEPROBABILISTIC ANALYSIS OFTHE PROJECT NETWORK 25 WEEKS 6,89 WEEKS 2,62 WEEKS EXPECTED TIME μ σ2 σ
- 14. EXAMPLEPROBABILISTIC ANALYSIS OFTHE PROJECT NETWORK 25 WEEKS EXPECTED TIME μ 30 WEEKS PROPOSED PROJECT TIME X WHAT IS THE PROBABILITY THAT THE SYSTEM WILL BE READY BY THAT TIME? WHAT IS THE PROBABILITY THAT THE SYSTEM WILL BE READY BY THAT TIME?
- 15. EXAMPLEPROBABILISTIC ANALYSIS OFTHE PROJECT NETWORK Z = X – μ σ 30 WEEKS 25 WEEKS 2.62 - = 1.911.91
- 16. EXAMPLEACTIVITY EARLIEST ANDLATEST TIMES AND SLACK z = 1.91
- 17. EXAMPLEACTIVITY EARLIEST ANDLATEST TIMES AND SLACK
- 18. EXAMPLEACTIVITY EARLIEST ANDLATEST TIMES AND SLACK 0.9719 probability of completing the project in 30 days 0.9719 probability of completing the project in 30 days
- 19. EXAMPLEACTIVITY EARLIEST ANDLATEST TIMES AND SLACK www.measuringusability.com
- 20. EXAMPLEACTIVITY EARLIEST ANDLATEST TIMES AND SLACK z = 1.91 97.19 %
Editor's Notes
- #3 CPM : A single estimates for activity times did not allow for any variation in activity times Activity times were treated as if they were known for certain PERT: multiple time estimates allow for variation in activity times