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CAPM Practice: Demonstrate an understanding of a project management plan schedule

Question 50 of 85 in Demonstrate an understanding of a project management plan schedule

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A project activity has three expert estimates: Optimistic = 4 days, Most Likely = 6 days, Pessimistic = 14 days. Using PERT, what is the expected duration?

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Correct answer: 7 days

Explanation

PERT = (O + 4M + P) / 6 = (4 + 4×6 + 14) / 6 = (4 + 24 + 14) / 6 = 42/6 = 7 days. The pessimistic estimate (14 days) pulls the expected duration above the most likely estimate (6 days), reflecting schedule risk. The PERT formula weights the most likely estimate four times more than the optimistic or pessimistic.

**Why not A:** Nine days would result from an incorrect calculation. Applying the PERT formula (4 + 24 + 14) / 6 = 42 / 6 = 7 days, not 9. A result of 9 might come from miscalculating the weighted components or using an incorrect formula.

**Why not B:** Six days is simply the most likely estimate without applying the PERT formula. PERT accounts for uncertainty by incorporating the optimistic and pessimistic estimates, which in this case pulls the expected duration above the most likely value due to the skewed pessimistic estimate of 14 days.

**Why not D:** Eight days is the result of using the triangular distribution formula (O + M + P) / 3 = (4 + 6 + 14) / 3 = 24 / 3 = 8. The PERT formula weights the most likely estimate four times, producing a different result of 7 days.

Key Concept

This question covers Demonstrate an understanding of a project management plan schedule under Demonstrate an understanding of a project management plan schedule (Predictive, Plan-Based Methodologies).

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