Estimating Work Duration

1. Determine the availability of the resources
2. Show the availability as a percentage of the effort required to achieve the work package
3. Duration = (Effort/Productivity)/Availability

▫        If effort is in # of hours, the duration will be in # of hours

▫        To have duration in days, divide the value calculated above by the number of working hours per day

4. Cost = Duration* Unit cost

▫        Cost = (Effort/Productivity ) * Unit cost

▫        Determine duration as per number 3 above

▫        Unit  cost : e.g. $40/hour

Determining Durations of Work packages

•        PERT of each work package:

              

•        PERT of the entire project is the sum of the PERTs of all the activities on the critical path

•        Standard Deviation of a work package:

              

PERT, Sigma and probabilities

•        50% probability that a task’s duration equals its PERT

•        68% probability that a task’s duration is between ( PERT + 1 * Sigma) and (PERT – 1 * sigma)

•        95% probability that a task’s duration is between ( PERT + 2 * Sigma) and (PERT – 2 * sigma)