Help please for this question from Oliver Lehmann
Submitted by sunitaPMP on Mon, 12/10/2012 - 01:38
Can someone help me with this question?
Q94-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, what is the duration uncertainty of the
entire path?
o 21 days
o 30 days
o 42 days
o No statement is possible from the information given
Forums:
rajesh.thallam
Mon, 12/10/2012 - 02:38
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Answer B
As mentioned in the question,
Uncertainity = Tp-To
We know that
Sigma (Standard deviation or SD) = (Tp-To)/6
For activity 1, SD = 18/6 = 3 => Variance = 9 (V = SD^2)
For activity 2, SD = 24/6 = 4 => Variance = 16
Remember, to calculate standard deviation for the complete path,
SD = sqrt(V1 + V2)
SD = sqrt(16+9)
SD = 5
Duration Uncertainity, (Tp-To) = 6 * SD = 30 days
Hope, I was clear.
sunitaPMP
Mon, 12/10/2012 - 02:57
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Thanks for the
Thanks for the answering.Where can I find these details? in PMBOK ?
rajesh.thallam
Mon, 12/10/2012 - 03:26
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Rita's
I don't think PMBOK covers this in detail. Refer Rita's PMP Exam Prep (Pg 191/192)
http://www.deepfriedbrainproject.com/2010/08/standard-deviation-project-estimates.html