Project Management Professional (PMP) Practice Exam

Together with your team, you applied three-point estimation on a critical path which consists of two activities. The following duration uncertainties are all calculated assuming a ±3sigma confidence interval. The duration uncertainty—defined as pessimistic minus optimistic estimate—of the first activity is 18 days; the second estimate has an uncertainty of 24 days. Applying the PERT formula for paths (beta distribution), what is the duration uncertainty of the entire path?

1. 21 days

2. 30 days

3. 42 days

4. No statement is possible from the information given.

The correct answer is: 30 days

The duration uncertainty of the first activity is 18 days and the second activity is 24 days. When calculating the duration uncertainty for the entire path, we combine these two uncertainties using the PERT formula which is (pessimistic + 4 x most likely + optimistic)/6. In this case, the most likely estimate for both activities is equal to the expected duration, so the formula becomes (optimistic + pessimistic)/2. Therefore, the duration uncertainty for the entire path would be (18 + 24)/2 = 42/2 = 21 days. Option A is incorrect because it only takes into account the uncertainty of the first activity. Option C is incorrect because it adds the uncertainties of both activities instead of averaging them. Option D is incorrect because the question specifically asks for the duration uncertainty of the entire path, which can be calculated based on the information provided. The correct