Project Management Professional (PMP) Exam Practice – Question1405

Activity A has a pessimistic (P) estimate of 36 days, a most likely (ML) estimate of 21 days, and an optimistic (O) estimate of 6 days. What is the probability that activity A will be completed in 16 to 26 days?


A.
55.70 percent
B. 68.26 percent
C. 95.46 percent
D. 99.73 percent

Correct Answer: B

Explanation:

Explanation:
First, compute the standard deviation:

Next, compute PERT expected time:

Finally, determine range of outcomes using 1:
21-5 = 16 days, and 21+5 = 26 days

Simply defined, 1 is the amount on either side of the mean of a normal distribution that will contain approximately 68.26 percent of the population. Meredith and Mantel 2012, 348-350