Time Estimation

Task Best case Worst case Result
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Best case
Set the minimum time needed for this step.
Worst case
Set the absolute maximum of time.
Which unit?
It doesn't matter if days, month or dollar. Just use the same unit everywhere.
How is it calculated?
(Best case + (Worst case ✕ 2)) / 3
Why emphasizing the worst case?
Things often take longer than expected and things rarely take shorter than expected.