Project Management

Project Task Duration Estimation and Scheduling

PMI NC Piedmont Triad Chapter, and Kim H. Pries

Topics: Cost Management, Estimating, Risk Management, Schedule Management, Scheduling, Scope Management, Work Breakdown Structures (WBS)

Our experience suggests that insufficient time spent on schedule development is a key risk to project success. A little research in printed material or on the internet should confirm this hypothesis.

Is it always guess work?
Project estimation does not have to be new or novel to the executing or responsible parties on the project. Ultimately, estimation is and will always be an educated guess with some risk mitigation, which is supported by prior knowledge in the form of experience and perhaps historical record. As the team marches through the project, it will find that the uncertainties are consumed by duration of the project just as the arrival estimate of a GPS system becomes more accurate as we approach the target location.

Steps in estimating
Some information is essential to creating a meaningful estimate:

  • A statement of scope or scope document that defines what the project is and is not (this includes vetting of underlying assumptions and constraints)
  • A task list in the form of a work breakdown structure (WBS)
  • The task details defined (not simply a list of task names)
  • Duration estimations provided by the team and with use of historical record
  • Task dependencies (schedule and risks) clarified
  • Schedule risks identified, such as:
    • Critical Path? (longest consecutive, slack-less path)
    • Task variations
  • Planned schedule risk mitigation

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