Final answer:
In PERT, Optimistic Time, Pessimistic Time, and Most Likely Time are the three-time estimates used, while Expected Time is derived from these three and not independently evaluated.
Step-by-step explanation:
In PERT (Program Evaluation and Review Technique), there are three-time estimates used to calculate the expected duration of a project's activities: Optimistic Time, Pessimistic Time, and Most Likely Time. The fourth option listed, Expected Time, is actually derived from the other three estimates and is not an independent estimate provided by project managers. The Expected Time is calculated using a weighted average of the three-time estimates, where the Most Likely Time is given more weight compared to the Optimistic and Pessimistic Times.
PERT is a project management tool used to plan and control large-scale projects by defining the individual tasks and their duration. This technique is known for accounting for the uncertainty in project scheduling by considering the variance in time estimates.