Final answer:
PERT analysis uses a. pessimistic, b. most likely, and e. optimistic time estimates to calculate the expected time for project tasks and the entire project, aiding in project management.
Step-by-step explanation:
The Project Evaluation and Review Technique (PERT) analysis is based on three different time estimates for the completion of a project task: pessimistic time, most likely time, and optimistic time. These estimates are used to calculate the expected time for each task and, by extension, the entire project. PERT is a statistical tool that helps in planning, organizing, and controlling large projects by analyzing the tasks involved and estimating the shortest possible time in which the entire project can be completed.