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TOPIC: PERT/Standard Deviation Question

PERT/Standard Deviation Question 2 years 9 months ago #14611

 Brandon A Topic Author Visitor Hi All, I've been working through some sample questions over at Oliver Lehman's PM site. I came a across #27 in his 100 free PMP questions. I come from a quality background where we determine standard deviation empirically from a data set so these equations to approximate variance and SD are working a part of my brain that must be dormant. How do we arrive at 5.2 from the data set given? Any help is appreciated, see the problem below. Thanks! A project manager made 3-point estimates on a critical path along a sequence of activities A through E and found the following results: Assuming ±3 sigma precision level for each estimate, what is the calculated standard deviation of the allover path? App. 4.2 days App. 5.2 days App. 6.2 days You can not derive the path standard deviation from the information given. Your e-mail address will never be displayed on the site. Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable. Last edit: by Rochelle Martinez.

PERT/Standard Deviation Question 2 years 9 months ago #14646

 Kunwar Goyal Offline Fresh Boarder Posts: 1 Thank you received: 0 hi, there will no influence of the activity ,if we choose activity B,C and D so calculate the SD for A and E =((35-17)/6)+((24-12)/6)=3+2=5 Pl correct me if I am wrong Your e-mail address will never be displayed on the site. Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.

PERT/Standard Deviation Question 2 years 9 months ago #14677

 Brandon A Topic Author Visitor Me again, I found a similar problem and explanation which helped me figure out this one. You must first calculate the standard deviations of each sequence activity, A through E, using (P-O)/6. Square each standard deviation to yield the variance (Variance = SD^2). Add all the sequence activity variances together then take the square root of the sum. This will yield 5.19... which rounds to 5.2. You could then express the schedule as 83.1 +/- 5.2 days. I just passed the PMP today but couldn't let this question go. Thanks Your e-mail address will never be displayed on the site. Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.

PERT/Standard Deviation Question 2 years 9 months ago #14679

 Anonymous Topic Author Visitor Thanks for clarifying Your e-mail address will never be displayed on the site. Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.

[email protected] 7 months 2 weeks ago #23294

 Anonymous Topic Author Visitor Thank you! It seems like the PERT weighted values in the table are included to throw us off! Your e-mail address will never be displayed on the site. Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.

[email protected] 6 months 4 weeks ago #23540

 Anonymous Topic Author Visitor I couldn't let it go either. Thank you. Your e-mail address will never be displayed on the site. Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.

PERT/Standard Deviation Question 4 months 2 weeks ago #24876

 Anonymous Topic Author Visitor in the question it state +/- 3 sigma Your e-mail address will never be displayed on the site. Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.

PERT/Standard Deviation Question 4 months 22 hours ago #25335

 Amit Kumar Offline Fresh Boarder Posts: 6 Thank you received: 0 Thank Brandon...was searching for this. Your e-mail address will never be displayed on the site. Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.
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