Duration Uncertainty refers to the idea that the actual duration of tasks may differ from their planned duration. When developing a schedule, durations of tasks planned with our best guess or what we believe is their Most-Likely duration estimate, representing the expected amount of time required to complete the work under normal conditions:
However, actual performance may vary. In some cases, work may be completed more efficiently than anticipated, resulting in a shorter duration. This shortest reasonable duration is referred to as the task’s Best-Case or Optimistic duration estimate:
Conversely, unforeseen challenges may cause the activity to take longer than expected. This longest reasonable duration is referred to as the task’s Worst-Case or Pessimistic duration estimate:
