Written by Get Ready For The PMP Exam
What Are Expected Activity Duration and Standard Activity Deviation?
Let’s say you have an activity on your projects activity list. How do you determine what the Expected Activity Duration (EAD) will be? For the PMP exam, you may want to know how to calculate it given a pessimistic estimate = 6 weeks, an optimistic estimate = 3 weeks, and a most likely estimate of 5 weeks. The formula for EAD is (P+4M+O)/6. We will plug in the estimates for (6+4*5+3)/6 weeks = 29/6 weeks = 4.8 weeks.
The Expected Activity Duration (EAD) according to the PERT calculation for this activity is 4.8 weeks. The question now is the standard deviation for this activity. You can use the pessimistic and the optomistic estimates for the standard deviation. The calculation is Standard Deviation = (pessimistic – optomistic)/6, or plugging in our data, SD = (P-O)/6, or (6-3)/6 weeks = 3/6 weeks = .5 weeks as the standard deviation.
The expected activity duration for this activity will be 4.8 weeks, with a standard deviation of .5 weeks, which would give you an estimated range of (4.8 + or – .5) = 4.3 to 5.3 weeks.
This is an overview of a couple of formulas needed on the PMP exam. For the best overview and explanation of all 49 formulas that you need refer to the PM Formulas
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Great information! I’ve been looking for something like this for a while now. Thanks!
i. Variances of the activities on the longest path of the project are 0.5, 0.3, 0.4 and 0.3. calculate the standard deviation of the project duration.