Project Management Essentials – Techniques for Estimating Activity Durations

Estimating activity duration is often overlooked when it comes to different ways that can be used to reach a better metrics on duration. To more accurately assess how long an activity takes it is necessary to take into consideration the skill-set and capabilities of the activity owner while incorporating different techniques.

Some of the most common scheduling techniques used for estimating activity duration as discussed below.

  1. Analogous Estimating – This technique is also known as “Top Down” estimating. A reference point should be set using similar previous projects that matches best with the activities for which we are running the estimates for.  Adjustments would need to be made for any differences.
  2. Parametric Estimating- Also known as “Rule of Thumb”, this technique takes statistical relationship between historical data and other variables into consideration. For example: If a resource can finish testing 100 lines of code in an hour, it will take 10 hours to test 1000 lines of code.
  3. Three-Point Estimates (PERT – Performance Evaluation & Review Tool) – This is one of the most widely used estimating technique wherein three different points of references in terms of case-based scenarios are established and  calculated according to the formula. The three metrics are established according to the “Most likely”, “Optimistic (best-case)” and “Pessimistic (worst-case)” scenario. PERT = [Optimistic + (4 x Most Likely) + Pessimistic]/6
  4. Reserve Analysis – This technique takes into consideration the uncertainties that could surround the project work. A contingency reserves is added to the schedule in case of any adversities like bad weather, earthquake, political instability, etc.