In PERT, which statement best describes best-case and worst-case estimates and how PERT uses them?

• A. Best-case corresponds to optimistic estimates; worst-case to pessimistic estimates; PERT uses a weighted average of optimistic, most likely, and pessimistic values.
• B. Best-case is the most likely outcome; worst-case is the minimum outcome.
• C. Best-case and worst-case are the same as most likely.
• D. PERT ignores optimistic estimates.

Answer: (A)

In PERT, estimates for an activity include optimistic (best-case), most likely, and pessimistic (worst-case) durations to account for uncertainty. The best-case and worst-case values are the optimistic and pessimistic estimates, and the expected duration is calculated as a weighted average that emphasizes the most likely outcome: E = (O + 4M + P) / 6. This setup captures a range of possible times while giving more weight to what is most probable, rather than simply averaging the extremes. The optimistic and pessimistic estimates inform the range and risk, but the final estimate centers on the most likely duration.