4.02A

Reserve Analysis

Duration estimates may include contingency reserves, (sometimes referred to as time reserves or buffers) into the overall project schedule to account for schedule uncertainty. The contingency reserve may be a percentage of the estimated activity duration, a fixed number of work periods, or may be developed by using quantitative analysis methods.

Project Management Software

Has the capability to help plan, organize, and manage resource pools and develop resource elements

Three-point Estimates

The accuracy of activity duration estimates can be improved by considering estimation uncertainty and risk. This concept originated with the Program Evaluation and Review Technique (PERT). PERT uses three estimates to define an approximate range for an activity's duration: Most Likely(tM) The duration of the activity, given the resources likely to be assigned, their productivity, realistic expectations of availability for the activity, dependencies on the other participants, and interruptions. Optimistic (tO) The activity duration is based on analysis of the best-case scenario for the activity. Pessimistic (tp) The activity duration is based on analysis of the worst-case scenario for the activity. PERT analysis calculates and Expected (tE) activity duration using a weighted average of these three estimates: tE=(tO+4tM+tP)/6 Duration estimates based on this equation may provide more accuracy, and the three points clarify the range of uncertainty of the duration estimates.

Optimistic (tO)

The activity duration is based on analysis of the best-case scenario for the activity.

Pessimistic (tp)

The activity duration is based on analysis of the worst-case scenario for the activity.

Most Likely(tM)

The duration of the activity, given the resources likely to be assigned, their productivity, realistic expectations of availability for the activity, dependencies on the other participants, and interruptions.

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. Activity durations can be quantitatively determined by multiplying the quantity of work to be performed by labor hours per unit of work.

Analogous Estimating

Uses parameters such as duration, budget, size, weight and complexity, from a previous, similar project, as the basis for estimating the same parameter or measure for a future project.

Bottom-Up Estimating

When an activity cannot be estimated with a reasonable degree of confidence, the work within the activity is decomposed into more detail. The resource needs are estimated. These estimates are then aggregated into a total quantity for each of the activity's resources. Activities may or may not have dependencies, this pattern of resource usage is reflected and documented in the estimated requirements of the activities