PERT Question

Submitted by Sunil on Thu, 03/29/2012 - 10:29

Hi,


The below question apperas in one of the Mock PMP exams by Christopher Scordo.


You have run away and joined the carnival as a project manager and are in charge ofconstructing the Ferris wheel in each town the carnival visits. However, this is somethingyou have never done before and you are getting different opinions from others on how longit takes. Joe, is new and has given you what you believe to be an optimistic estimate of 3hours, Bill says it will take 10 hours, which seems too long to you and quite pessimistic. Lastly, Margie, who is the most experienced at this task is telling you it will take 8 hours. You are not sure who to believe, so you decide to do a PERT estimation, based on this you have determined it will take how many hours to assemble the Ferris wheel.


A. 5 hours


B. 8 hours


C. 21 hours


D. 7 hours



Ans:
A - The PERT formula is Estimate= (Optimistic + (Most Likely *4) + Pessimistic)/6 [Project Time Management]


Although the answer is given as A - 5 hours, when I calculate , I am getting 7.5 hours and not 5.


ie, (3 + 8*4 + 10)/6 = 45/6 = 7.5


Am I missing anything here?


Thanks


Sunil

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Samir

Thu, 03/29/2012 - 11:50

Yeah, your calculation looks to be correct.

krantikumar50

Thu, 03/29/2012 - 13:24

Your answer looks to be correct. What reasoning does Christopher give for this analysis. KK.....

Sunil

Fri, 03/30/2012 - 05:56

He has given only the formula as reasoning.


Ans. A - The PERT formula is Estimate= (Optimistic + (Most Likely *4) + Pessimistic)/6 [Project Time Management]


The interesting thing here is that 7.5 hours is not even given as an option. Probably it could be a mistake, but I remeber reading a similar question on PERT somewhere else where my calculated value was not given as the correct answer. That is why I posted this question to see if I am really missing  anything.  

pmp_man

Fri, 03/30/2012 - 17:19

I did also recall, in the actual PMP exam you have some choice where the decimal value can be ignored. In project managment planning cannot be 100% accurate so there are some variances like +/- 10%. Here you can choose 7.5 the closest.