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Tolls and Techniques of Activity Duration Estimating

Expert Judgment

Expert with specialized knowledge of estimation and experience in similar projects may be used for Activity duration estimate.

Analogous Estimating

Analogous duration estimating technique uses the actual durations of a previous similar activity as the basis for estimates the duration of a future activity. This is typically used when available information about the project in very limited to prepare detailed estimates.

Parametric Estimating

Parametric Estimation is a technique in which durations can be determined by multiplying the ‘quantity of work’ to be performed by the ‘productivity rate or duration per unit of quantity’. For example, if one box can b assembled in 2hour,100 boxes can be assembled in 200 hours.

Three Point Estimates

Three-point estimates are based on determining three types of estimates,Optmistic,Most Likely

And Pessimistic (worst- case).

An Activity duration estimate can be determined by using an average of the three estimated durations, i.e. optimistic, pessimistically and most likely. That average will often provide a more accurate duration estimate than single point(most-likely)estimate.

Program Evaluation & Review Technique (PERT) may also  be used to determine estimates.

PERT Estimate=(Optimistic + 4*Most Likely+Pessismistic)/6

Standard Deviation=(Pessimistic-Optimistic)/6^2

Variance =(( Pessimistic-Optimistic)/6)^2

Reserve Analysis

All identified risks and their impact is considered while estimating the duration estimates. An additional time is added to project duration estimates, which is known as contingency reserves, time reserves or buffers. This contingency reserve can be a percentage activity duration, a fixed umber of work periods, or developed by quantitative risk analysis. As estimation process proceeds and team have more detailed information, the contingency reserve can be used completely or partially, or can later reduce or eliminated.

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