Duration
DE: Dauer
The total work periods required to complete an activity.
Detailed Explanation
Duration is the total number of work periods required to complete an activity, expressed in hours, days, or weeks. It is different from effort — a task requiring 16 hours of effort may have a duration of 2 days (one person) or 1 day (two people working in parallel).
Duration estimates are critical inputs to the project schedule. Common estimation techniques include analogous estimating (using similar past projects), parametric estimating (using statistical relationships), three-point estimating (optimistic, most likely, pessimistic), and bottom-up estimating.
Accurate duration estimation requires understanding resource availability, skill levels, and potential risks. Over-optimistic estimates are the leading cause of schedule overruns. Always include contingency based on risk analysis.
Key Points
- Measured in work periods (hours, days, weeks)
- Different from effort — duration depends on resource allocation
- Estimation techniques: analogous, parametric, three-point, bottom-up
- Critical input to the project schedule model
- Resource availability and skill levels affect duration
- Over-optimism is the leading cause of schedule overruns
Practical Example
A team estimates a database migration task. Analogous estimate from last project: 10 days. Three-point: optimistic 7 days, most likely 10 days, pessimistic 18 days. PERT calculation: (7 + 4*10 + 18) / 6 = 10.8 days. The PM uses 11 days and adds 2 days contingency for the identified risk of data quality issues.
Tips for Learning and Applying
Always distinguish between effort (person-hours) and duration (calendar time)
Use three-point estimating for activities with high uncertainty
Get estimates from the people who will do the work
Track actual vs. estimated duration to improve future estimates
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