RCDD · Question #174
What is the PERT estimate (in hours) for project design where: - Optimistic time is 40 hours - Most likely time is 50 hours - Pessimistic time is 60 hours
The correct answer is C. 50 hours. The PERT formula - (Optimistic + 4 x Most Likely + Pessimistic) / 6 - yields (40 + 200 + 60) / 6 = 50 hours.
Question
What is the PERT estimate (in hours) for project design where:
- Optimistic time is 40 hours
- Most likely time is 50 hours
- Pessimistic time is 60 hours
Options
- A40 hours
- B45 hours
- C50 hours
- D55 hours
- E60 hours
How the community answered
(37 responses)- A3% (1)
- B3% (1)
- C73% (27)
- D16% (6)
- E5% (2)
Why each option
The PERT formula - (Optimistic + 4 x Most Likely + Pessimistic) / 6 - yields (40 + 200 + 60) / 6 = 50 hours.
40 hours is only the optimistic estimate; it ignores the most likely and pessimistic values entirely and is not a weighted average.
45 hours does not result from the standard PERT three-point estimation formula applied to these inputs.
Applying the PERT formula: (40 + 4x50 + 60) / 6 = 300 / 6 = 50 hours. The formula weights the most likely estimate four times more heavily than the optimistic and pessimistic values to reflect its higher probability of occurrence, resulting in a weighted average of 50 hours.
55 hours does not result from the standard PERT three-point estimation formula applied to these inputs.
60 hours is only the pessimistic estimate; it ignores the optimistic and most likely values entirely and is not a weighted average.
Concept tested: PERT three-point duration estimation formula
Source: https://www.pmi.org/pmbok-guide-standards/foundational/pmbok-guide
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