Estimate Activity Durations
Estimate Activity Durations is the process of estimating the number of work periods needed to complete individual activities with the estimated resources.
Explanation
Estimate Activity Durations is the process of approximating how long each schedule activity will take to complete given the assigned resources, resource capabilities, and known constraints. Duration estimates are typically expressed in work periods (hours, days, weeks) and account for the amount of effort required and the availability of resources.
This process uses several estimating techniques, including analogous estimating (using historical data from similar activities), parametric estimating (using statistical relationships), three-point estimating (using optimistic, most likely, and pessimistic estimates), and bottom-up estimating (aggregating estimates from lower-level components). The choice of technique depends on the amount of information available and the desired accuracy.
Estimate Activity Durations is an iterative process that becomes more accurate as the project progresses and more detail is known. Early estimates may have wide ranges of uncertainty, which narrow as the project moves through planning and into execution. The process requires inputs from the activity list, activity attributes, resource requirements, resource calendars, and risk register. Estimates should include an indication of the range of possible results, such as a duration of 10 days plus or minus 2 days.
Key Points
- •Estimates the number of work periods to complete each activity
- •Uses analogous, parametric, three-point, and bottom-up estimating techniques
- •Accuracy improves progressively as more information becomes available
- •Estimates should include an indication of the range of uncertainty
Exam Tip
Duration estimates are based on assigned resources. If you change the resource assignment, the duration estimate may change. More resources do not always mean shorter duration.
Frequently Asked Questions
Related Topics
Analogous Estimating
Analogous estimating uses historical data from similar past activities or projects as the basis for estimating the duration or cost of a current activity or project.
Parametric Estimating
Parametric estimating uses a statistical relationship between historical data and other variables to calculate an estimate for activity parameters such as cost, budget, and duration.
Three-Point Estimating (PERT)
Three-point estimating uses three estimates (optimistic, most likely, and pessimistic) to define an approximate range for an activity's duration or cost, improving accuracy by considering estimation uncertainty.
Bottom-Up Estimating
Bottom-up estimating is a method of estimating project duration or cost by aggregating the estimates of the lower-level components of the work breakdown structure.
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