easyMultiple Choice
PK0-005 Practice Question: A project team is estimating the duration of a…
A project team is estimating the duration of a task. The optimistic estimate is 4 days, the pessimistic is 12 days, and the most likely is 6 days. Using the three-point estimating technique (PERT), what is the expected duration?
⚠ Common exam trap
The trap here is that candidates often mistakenly use a simple average or the midpoint of the range instead of the weighted PERT formula, leading to incorrect answers like 7.33 or 8 days.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
6.67 days
The PERT expected duration formula is (Optimistic + 4 × Most Likely + Pessimistic) / 6. Plugging in the values: (4 + 4×6 + 12) / 6 = (4 + 24 + 12) / 6 = 40 / 6 = 6.67 days. This weighted average accounts for uncertainty by giving more weight to the most likely estimate.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
7.33 days
Why it's wrong here
PERT weights the most likely estimate fourfold: (4 + 4×6 + 12) ÷ 6 = 40 ÷ 6 ≈ 6.67 days, not 7.33. This figure arises from misapplying the weighting, perhaps treating the most likely value as double-counted rather than quadrupled.
- ✗
8 days
Why it's wrong here
Eight days is the arithmetic mean of the three estimates (4 + 6 + 12) ÷ 3, not the PERT weighted result. PERT quadruples the most likely value, giving (4 + 24 + 12) ÷ 6 ≈ 6.67 days.
- ✓
6.67 days
Why this is correct
PERT weights the most likely estimate fourfold: (4 + 4(6) + 12) / 6 = 40 / 6 = 6.67 days. This beta-distribution formula satisfies the stem's three-point estimating requirement, yielding the expected duration from optimistic, pessimistic, and most likely values.
- ✗
6 days
Why it's wrong here
Six days is simply the most likely estimate, ignoring the optimistic and pessimistic values entirely. PERT requires the weighted average formula (O + 4M + P) ÷ 6, which yields approximately 6.67 days, not the single modal figure.
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Written by Johnson Ajibi, MSc IT Security
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