Estimate activity durations

Key points

  • Analogous estimation – Comparing with a past similar activity. I have traveled to the nearest city once in the past and I took 2 hours. I am travelling again today, and I consider 2 hours as my estimate.
  • Parametric estimation – Average of multiple similar activities (index). I have traveled to the nearest city 20 times in the past and I am traveling again. I am taking an average of these twenty occurrences from the past and considering it as my estimate. Parametric is always more accurate than analogous
  • Three point estimation – (O+P+M)/3  or (O+4xM+P)/6. For every activity optimistic, pessimistic and most likely values are estimated and from these values a single point value is arrived at using one of the above formulas.
  • Bottom up estimation – Adding up activity level estimates and tallying with the work package level estimates
  • Alternatives analysis. For example : manual testing Vs automated testing, normal curing Vs steam curing, swimming pool Vs club membership.
  • Reserve analysis (buffer) – Amount of management and contingency reserves required for the project
  • Law of diminishing returns – Example – after a limit, adding more resources to a task will give minimal duration compression