More on Scheduling

Recap of Last Class Activity dependencies are shown through CPM/PERT Chart. Critical path Completion date Slack time in non-critical path activities Activity start and end dates and personnel responsibilities shown on Gantt Chart.

Managing Uncertainty Q: How confident can we be in our milestone dates and the delivery date? A: Using confidence and Statistics for each task, determine pessimistic and optimistic times if PT-OT is small for all tasks, then great!!! compute average PT-OT, and std dev if a task's PT-OT is outside the std dev, worry about that task

Managing Uncertainty Q: Where do we schedule uncertainty time? A1: spread it out by bumping each milestone. used by Critical Path A2: lump it together as one activity at end. used by Critical Chain

Common PERT Problems Missing dependencies Misinterpretation

Example K – integration testing L – Install Software M – Write Manual N – Train Users K L MN

Example K – integration testing L – Install Software M – Write Manual N – Train Users But wait, we can shorten the project if we write the manual right after testing is finished. (L and M can be done in parallel.) So… K L MN

Example K – integration testing L – Install Software M – Write Manual N – Train Users But wait, the system needs to be installed before we can use it to train people. So… K L M N

Example K – integration testing L – Install Software M – Write Manual N – Train Users But what is that activity between dates 3 and 4? So… K L M N

Example K – integration testing L – Install Software M – Write Manual N – Train Users Dashed line is a dummy activity K L M N

Example Note: dummies not needed with "activity on node" graphs. K N M L K – integration testing L – Install Software M – Write Manual N – Train Users

Resource Leveling Activity Shifting to avoid using resources during a peak time. use slack in start and end dates Activity Splitting to shorten duration break activity into pieces when more resources are available Optimize the System, not individual tasks Leveling usually yields longer projects

Example What is the completion time? Since F is so long, what would be the completion time if we break it into two parallel parts of 2wks and 3wks? A 3wks B 2wk E 2wks C 2wks F 5wks G 3wks H 3wks I 2wks D 2wks

Theory of Constraints “The Goal” by Goldratt in 1997 Traditional approach is to divide and divide into manageable parts, then optimize these parts. TOC looks at the whole system. 1.Identify: In order to manage a constraint, it is first necessary to identify it. 2.Exploit: Focus on how to get more production within the existing capacity limitations. 3.Subordinate: Prevent the materials needed next from waiting in a queue at a non-constraint resource. 4.Elevate: If, after fully exploiting this process, it still cannot produce enough products to meet market demand, find other ways to increase capacity. 5.Go back to Step 1.

Scheduling Tools Gantt Chart producers MS Project Web access Supports multiple projects Dependencies Billing support Resources leveling Gantt charts, activity network, …

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Open WorkBench

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