Process: Estimate Activity Durations
Process Group: Planning
Knowledge Area: Project Schedule Management
Purpose
The Estimate Activity Durations process involves approximating the number of work periods required to complete each activity, considering the resource types, quantities, productivity levels, and known constraints. This process provides the foundation for developing a realistic project schedule.
Inputs
- Project Management Plan – Especially the schedule management plan and scope baseline.
- Project Documents – Includes activity list, attributes, resource requirements, resource calendars, and lessons learned.
- Enterprise Environmental Factors (EEFs) – Historical duration data, productivity metrics, and organizational standards.
- Organizational Process Assets (OPAs) – Estimating templates, previous project data, and expert resources.
Tools and Techniques
- Expert Judgment – Used to estimate based on experience with similar activities.
- Analogous Estimating – Uses historical data from similar projects to estimate duration.
- Parametric Estimating – Uses statistical relationships between variables (e.g., quantity and duration).
- Three-Point Estimating – Uses optimistic, most likely, and pessimistic estimates to account for uncertainty.
- Bottom-Up Estimating – Aggregates estimates of lower-level components.
- Data Analysis – Includes reserve analysis to accommodate schedule risk.
- Decision Making – May involve team-based estimation or consensus techniques.
- Meetings – Collaboration sessions to validate and finalize duration estimates.
Outputs
- Duration Estimates – Quantified timeframes (e.g., days, weeks) for each activity, often with a range or confidence level.
- Basis of Estimates – Documentation explaining the assumptions, data sources, and methods used.
- Project Document Updates – Updates to activity attributes and assumption log based on the estimation process.
Role in the Process Group and Knowledge Area
- As part of the Planning Process Group, Estimate Activity Durations ensures time is realistically allocated before sequencing and scheduling.
- In Project Schedule Management, it supports the creation of accurate and defensible timelines.
Why It Matters
- Supports Accurate Scheduling – Helps develop a realistic and achievable project timeline.
- Accounts for Uncertainty – Encourages the use of multipoint estimates to reflect variability and risk.
- Improves Resource Planning – Informs when and how long resources will be needed.
- Builds Confidence – Stakeholders trust schedules that are based on sound estimation methods.