Confusing - pls clarify

Submitted by dipti1pmp on Tue, 11/25/2014 - 13:16

James has been managing a hotel construction project in a busy street. He is in the process of estimating activity durations for building walls and calculates the most likely estimate as 15 days. If pre-fabricated material is used, it would take no more than 12 days to finish the work. However, the work may be delayed and could take up to 18 days if less experienced construction workers are used to build the walls. But, the engineer in-charge of the work estimates the duration as 8 days when pre-fabricated material is used. What is the expected duration of building walls using the three-point (PERT) estimate, if the engineer's estimation is assumed correct?

A.   12 days

B.   11 days

C.   16 days

D.   14 days

 

i got ans 12 days but it is not rather 14

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hkakumanu@gmail.com

Tue, 11/25/2014 - 16:22

(P+4M+O)/6 =  (8+4*15+18)/6 = 14.33 i.e., 14 days.

dipti1pmp

Wed, 11/26/2014 - 05:39

from sentence:

 If pre-fabricated material is used, it would take no more than 12 days to finish the work. 

m=12?

 

jwhelan

Tue, 11/25/2014 - 17:08

PERT uses weighed average three point estimated. thats the beta calculation not the triagular. so we take the new 8 optimistic, 4 times the most likely 15 plus the pessimistic 18 and divide by 6.

 

thats  O+4M+P / 6 = PERT

         8 + 4(15)+18 / 6 = PERT

         8 + 60 + 18 / 6 = PERT

                             14  = PERT

dipti1pmp

Wed, 11/26/2014 - 05:38

reading sentence:  If pre-fabricated material is used, it would take no more than 12 days to finish the work. 

 

will not m=12?

 

 

ovhirup

Wed, 11/26/2014 - 07:43

Answer

You need to chosse the best answer.

Now assumption is "if the engineer's estimation is assumed correct"

that is 8 NOT 12.

so Three point estimation goes = (8+15+18)/3=41/3=13.6667

 

We choose the best answer , that is 14 , D

 

 

dipti1pmp

Wed, 11/26/2014 - 08:28

we must be using the =p+4m+6o /6 right?

dipti1pmp

Wed, 11/26/2014 - 08:29

sorry that was p+4m+o / 6

 

 

ovhirup

Wed, 11/26/2014 - 11:46

 


　


PERT Beta 3-point = (Pessimistic + (4 * Most Likely) + Optimistic) / 6


PERT Triangular 3-point = (Pessimistic + Most Likely + Optimistic) / 3


 


The question should mention what type of estimation is being asked.


I assumed PERT Triangular 3-point , The question is not complete, it should mention the estimation technique.

dipti1pmp

Wed, 11/26/2014 - 12:46

when the question does not mention we must be using the weightd beta

ovhirup

Wed, 11/26/2014 - 13:39

So using Beta estimate


 


PERT=(8+4*15+18)/6= 86/6= 14