Estimate Activity Durations 101

What Does Estimate Activity Durations Involve and When Do You Perform It in a Project Life Cycle?

• WHAT Estimate Activity Durations Is.  Estimate Activity Durations implies forecasting the number of all human resources and materials needed to complete each activity of the project and then trying to estimates work effort, work resources, and number of work periods required to complete each activity, with progressive elaboration.
• WHY Estimate Activity Durations Is Important. Activity duration estimates are paramount inputs for the project schedule model.
• WHEN Estimate Activity Durations Is Executed. A project manager performs the schedule management activities processes in this order: Define Activities, Sequence Activities, and Estimate Activity Durations. Henceforth, activity durations are estimated after knowing what resources are available and before developing project schedule.
• HOW Estimate Activity Durations Operates.

Source: PMBOK® Guide, 6th ed., Chapter 6, section 6.4, p. 195.

Estimate Activity Durations Key Terms

What Are the Key Terms to Fully Understand the Process of  Estimating Activity Durations?

• Activity Duration Estimate. A quantifiable estimate expressed as the number of work periods needed to complete a schedule activity.
• Activity Resource Requirements. The resources required to complete the activities in the activity list.
• Alternative Analysis. Figuring out all of the possible different ways a potential outcome may be achieved and then making a decision about which method is best.
• Analogous Estimating. An estimating process that bases estimates upon similar activities with similar resource category and types from a similar type of projects executed earlier. Also called top-down  estimating.
• Bottom-Up Estimating. The process of breaking down an activity into smaller pieces, then rolling up the estimates upwards to the level of the original activity to arrive at a total cost.
• Parametric Estimating. An estimating technique that uses statistical techniques to calculate cost or duration values for activities based on data from similar earlier projects.
• Published Estimating Data. A database of known quantities or costs related to completion of activities in the project.
• Reserve Analysis. An analytical technique that takes care of uncertainty by adding extra time – also called buffers or time reserves – to the schedule or extra cost, as either contingency or management reserves.
• Resource Breakdown Structure. A breakdown of the resources required to complete the project, by category and type.
• Resource Calendar. The specific time period when a resource is available and scheduled to be used on the project.
• Resource. People, equipment, locations, or anything else that a project manager needs in order to do all of the activities planned.
• Risk Register. The documented list of all identified risks on the project and their characteristics.
• Three-Point Estimate. A formula that takes into consideration uncertainty factor when it calculates a weighted average of the optimistic, most likely, and pessimistic estimates.
• Work Periods. The activity duration estimates, usually expressed in hours or days – for smaller projects – or in weeks or months – for larger projects.

Estimate Activity Durations Tips

What Are the Best Tips to Answer Correctly the PMP Cerification Exam Questions on Estimate Activity Durations Process?

• Breakdown Structures. On the PMP exam, you will find the following four breakdown structures:
  • work breakdown structure (WBS)
  • organizational breakdown structure
  • resource breakdown structure
  • risk breakdown structure.
• Contingency Reserves Vs. Management Reserves. Contingency reserves are meant for known unknowns and are included in the schedule baseline, whereas management reserves are meant for unknown unknowns – unforeseen work that is within the scope of the project – and are not included in the schedule baseline.
• Duration Estimate Vs. Effort Estimate. The duration of an activity is the amount of time that activity takes, while the effort is the total number of person-hours expended.
• Estimators. For small projects the estimators are those who will be doing the work; for larger projects, the estimators should be members of the project team.
• Leads and Lags. The activity duration estimates do not include leads and lags, only the estimates for each project activity.
• Physical Vs. Financial Resources. The activity resource requirements include only physical resources, not financial ones.

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