Estimate Activity Durations Process

Posted on March 9, 2009 by


Estimate Activity Durations is one of the 42 project management processes outlined in the fourth edition PMBOK®. It’s categorized as one of the six Time knowledge area processes, and one of the twenty Planning processes.

The purpose of this process is straightforward—it estimates how long the individual project activities will take. We first need a list and information about these activities, which is in the form of the Activity List and Activity Attributes documents (outputs of the Define Activities process). We also should know the resource requirements, which is in the form of the Activity Resource Requirements document (an output of the Estimate Activity Resources process), and we must know how much time people have to work and when they are available, and this is in the form of the Resource Calendars (an output of the Acquire Project Team process). Estimate Activity Durations lists four different ways to actually estimate how long an activity will take—Expert Judgment, Analogous Estimating, Parametric Estimating, and Three-Point Estimating. Also, the tool of Reserve Analysis may be used to add a little time into your estimates as a safety, so that the entire project will not be behind schedule if some activities take longer than planned. To read more about these tools, please see earlier postings on TAPUniversity’s blog: PMP Exam – PERT Formula (posted February 6, 2009) which is a weighted three-point estimating formula; Reserve Analysis (posted February 11, 2009); and PMP Exam – Cost Estimating Tools and Techniques (posted February 4, 2009). The primary output of Estimate Activity Durations is the Activity Duration Estimates, which is then used to develop the project schedule in the Develop Schedule process.