Expert with specialized knowledge of estimation and experience
in similar projects may be used for Activity duration estimate.
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 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
Variance =(( Pessimistic-Optimistic)/6)^2
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