One of my preferred estimation techniques, especially when combined with bottom-up estimation is the PERT Estimation formula.
Program Evaluation and Review Technique (PERT) is a project management method that uses three time estimates for each activity to calculate an expected duration for each project activity. The formula for estimating the expected duration (TE) using PERT is as follows:
TE=(O+4M+P)/6
Where:
- O is the optimistic time estimate (the best-case scenario).
- M is the most likely time estimate.
- P is the pessimistic time estimate (the worst-case scenario).
The formula takes a weighted average of the three estimates, giving more weight to the most likely estimate. This approach is useful for tasks that may have inherent uncertainty, and it aims to provide a more realistic estimate by considering both optimistic and pessimistic scenarios.
