This question-specific review guide is tied to the answer reasoning for a PracticeTestVault item. Use it after you answer the question so the review stays focused on what the prompt actually tested.
What this question is testing
Objective: Calculate PERT standard deviation and variance
Prompt focus: For a PERT estimate, optimistic duration is 8 days and pessimistic duration is 26 days. What are the activity standard deviation and variance?
Why the correct answer works
3 days and 9 square-days
PERT standard deviation = (P – O) / 6 = (26 – 8) / 6 = 3 days; variance = 3 squared = 9 square-days.
Why the tempting wrong answer fails
The tempting wrong answer usually loses because it skips the key condition, priority, or evidence in the prompt.
Plain-language takeaway
Use the rationale to connect the prompt clue, the correct choice, and the tested objective before retaking a similar item.
Simple analogy
Think of calculate pert standard deviation and variance like following a short checklist: identify the clue, confirm the rule, and then make the move that fits this exact scenario.
How to review it before a retake
- Underline the command word and name what the question is asking before rereading the choices.
- Compare the correct answer against the closest distractor and write the exact detail that separates them.
- Retest this objective with a fresh question without looking at the rationale first.