Comprehensive Project Management And Scheduling Techniques For Students Practice Test

In PERT, the expected duration is found by weighting the three point estimates so the most likely outcome has the most influence. The formula uses the optimistic time (O), the most likely time (M), and the pessimistic time (P) as TE = (O + 4M + P) / 6. The numbers 1, 4, and 1 add up to 6, so this is a weighted average that gives four times more weight to the most probable duration. This reflects the idea that projects are more often closer to the most likely case than to the extremes, while still accounting for uncertainty from the optimistic and pessimistic bounds. As for the assumed distribution, PERT uses a Beta distribution to model durations. The Beta is bounded between O and P and can be skewed toward the most likely value, which aligns with how people perceive project uncertainty. This is why a simple normal distribution isn’t used in PERT, since normal implies symmetry and unbounded tails, which doesn’t fit the bounded, skewed nature of project activity durations. The standard deviations in PERT are typically expressed in terms of the same bounds, often approximated as (P − O)/6, tying back to the same Beta-based modeling. So, the best answer uses the weighted average with four times the most likely duration and assumes a Beta distribution for durations.