Dear PM Advisor. Dec 16, 2013

Dear PM Advisor, When I schedule my activities in MS-Project, should I use best-case or worst case? Should I let people add a buffer to their activity durations? 

Protecting myself in New Jersey

Dear Protecting,

  • Never use best case since projects are bound to have problems and you will miss the deadlines you promised your management.
  • Never use worst case since your projects will always show due dates way beyond where management knows they should be.
  • Never allow people to add buffers to their activities since that will also result in completion dates too far in the future.

So what does that leave you? Most-likely case with the buffer added in at the management level, not the team level. Let me explain. First we'll talk about the number of tasks you add to your Work Breakdown Structure.

Say one of your activities is the coding of some software or the creation of some document. Best case would have you code the software and sell it. That never happens. You code, test, fix, test, then approve. Sometimes you go through three or four rounds of test and fix before you are happy with it. Same with documents. So your Work Breakdown Structure  needs to include all these steps:

  • Draft, review, edit, review, edit, approve.
  • Code, test, repair, test, repair, test, repair, test, approve

Whatever is common practice at your company should be planned for the current project.

Now we need to talk about buffers. When someone estimates the duration of their activities, they should give you the most likely case without a buffer. You add these all up according to the network to determine the overall project timeline. You present this to management. Since you have added all the 'known unknowns' as represented by the redo activites, you are done. At this point, management adds a buffer to take into account all the 'unknown unknowns.' They may choose to add 10 - 20% to the overall time required by the project.

You, the Project Manager, own this buffer. If someone requires an extra day to complete a task, you take it out of your buffer. If someone finishes an activity two days ahead of shedule, notify the next person down the line of the change in schedule and add these days to your buffer. And when the bad thing happens to your project and you need those extra two weeks, you have them there in the buffer.

Another time I'll address the subject of maintaining control of the buffer.

Good luck,

PM Advisor

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