Quick Answer
The answer is 16.67 days. This result comes from the PERT three-point estimate calculation, which uses the weighted average formula (Optimistic + 4×Most Likely + Pessimistic) / 6 to account for uncertainty in activity durations. By plugging in the given values—10 days optimistic, 15 days most likely, and 30 days pessimistic—you get (10 + 60 + 30) / 6 = 100 / 6, yielding 16.67 days. On the Certified Associate in Project Management CAPM exam, this question tests your ability to apply the beta distribution model for schedule estimation, a core concept in the Plan Schedule Management process. A common trap is mistakenly using a simple average (adding all three and dividing by three), which ignores the heavier weighting given to the most likely estimate. To avoid this, remember the mnemonic “O + 4M + P over 6” and that the “4” gives the most likely estimate four times the influence, reflecting real-world project uncertainty.
This CAPM practice question tests your understanding of predictive plan-based methodologies. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A project manager is creating the project schedule. The team estimates that the optimistic time for an activity is 10 days, the pessimistic time is 30 days, and the most likely time is 15 days. Using PERT three-point estimation, what is the expected duration?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
16.67 days
Correct calculation using PERT formula.
18.33 days
Why wrong: This might result from using a different formula.
20.00 days
Why wrong: This is the average of optimistic and pessimistic.
15.00 days
Why wrong: This is just the most likely time.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
16.67 days
The PERT three-point estimate formula is (Optimistic + 4×Most Likely + Pessimistic) / 6. Plugging in the values: (10 + 4×15 + 30) / 6 = (10 + 60 + 30) / 6 = 100 / 6 = 16.67 days. This weighted average gives more influence to the most likely estimate, reflecting a beta distribution.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
16.67 days
Why this is correct
Correct calculation using PERT formula.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
18.33 days
Why it's wrong here
This might result from using a different formula.
20.00 days
Why it's wrong here
This is the average of optimistic and pessimistic.
15.00 days
Why it's wrong here
This is just the most likely time.
Common exam traps
The trap here is that candidates often use a simple arithmetic mean (average) instead of the weighted PERT formula, leading them to select 18.33 days (Option B).
Detailed technical explanation
PERT (Program Evaluation and Review Technique) uses a beta distribution to model activity durations, where the formula (O + 4M + P)/6 approximates the mean. The standard deviation is (P - O)/6, which for this activity is (30-10)/6 = 3.33 days, allowing calculation of confidence intervals. In practice, this method is critical for high-uncertainty projects like software development or construction, where single-point estimates are unreliable.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the CAPM exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Predictive Plan-Based Methodologies — This question tests Predictive Plan-Based Methodologies — Read the scenario before looking for a memorised answer..
The correct answer is: 16.67 days — The PERT three-point estimate formula is (Optimistic + 4×Most Likely + Pessimistic) / 6. Plugging in the values: (10 + 4×15 + 30) / 6 = (10 + 60 + 30) / 6 = 100 / 6 = 16.67 days. This weighted average gives more influence to the most likely estimate, reflecting a beta distribution.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This CAPM practice question is part of Courseiva's free PMI certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CAPM exam.
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