Estimating Activity Durations

Estimating Activity Durations is a critical process in project scheduling that involves determining how much time each project activity will require. This estimation forms the basis for developing a realistic project schedule. In the PMI Scheduling Professional context, activity duration estimates are typically expressed in work periods (hours, days, weeks) rather than calendar time. These estimates consider the resources assigned to the activity and their productivity rates. Several techniques are used for estimating: 1. Expert Judgment: Relies on historical information and expertise of those familiar with similar activities. 2. Analogous Estimating: Uses durations from similar past activities, adjusted for complexity and scope differences. It's quick but may lack precision. 3. Parametric Estimating: Uses statistical relationships between historical data and variables (e.g., square footage in construction) to calculate durations. 4. Three-Point Estimates: Incorporates uncertainty by using optimistic (O), most likely (M), and pessimistic (P) scenarios. The PERT formula (O+4M+P)/6 produces a weighted average. 5. Bottom-up Estimating: Estimates smaller components of work and aggregates them upward. Key considerations include: - Resource Availability and Capability: Affects how quickly activities can be completed. - Risk Factors: Identified risks may require buffering. - Activity Constraints: Mandatory dates or resource limitations influence durations. - Progressive Elaboration: Estimates become more precise as the project evolves. The output of this process includes activity duration estimates and documentation of assumptions and constraints. These estimates feed into the schedule development process, critical path determination, and ultimately affect project baseline and completion date forecasts. PMI emphasizes that accurate duration estimation is essential for realistic scheduling and effective resource management throughout the project lifecycle.

Estimating Activity Durations is a critical process in project scheduling that involves determining how much time each project activity will require. This estimation forms the basis for developing a …

Concepts covered: Analogous Estimating, Parametric Estimating, Three-Point Estimating, Reserve Analysis, Alternative Analysis, Monte Carlo Simulation, Bottom-Up Estimating, Expert Judgment, Learning Curve Analysis