Question on Scedule Diagram

Submitted by cplusplus on Fri, 05/14/2010 - 09:09


Please refer to the diagram above. Which of the following situations can this diagram represent?


 
 
  Choice 1  Task X (actual work of writing) and Task Z (thinking about what to write) should be done in parallel. 
 
  Choice 2  Task Z (unit testing the code) should begin 7 days after finishing Task X (writing the code). 
 
  Choice 3  Task X and Task Z together have 7 days of slack. 
 
  Choice 4  Task Z (plastering the floor) should begin 7 days after beginning Task X (pouring concrete). 


 


Please also briefly explain .....

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manuspmp

Fri, 05/14/2010 - 09:34

Choice 2  Task Z (unit testing the code) should begin 7 days after finishing Task X (writing the code).  should be the correct answer... As per the attached diagram.. 
  
 

The PMP Guru's picture

The PMP Guru

Fri, 05/14/2010 - 11:54

Hi,

** The Source Node Task X has no Predecessor as we can see.

** Basically 7 Days is the Job Duration for Task X.

** If I Use a Forward Pass:

--ES=1 of Task X.

--EF=7 of Task X.

--ES=8 of Task Z.

 

I hope It's clear.

Kind regards,

The PMP Guru.

http://thepmpguru.wordpress.com/

 

 

 

 

ChandraR

Fri, 05/14/2010 - 12:39

PMP guru:


I believe your interpretation is incorrect.  You are making assumptions about ES, EF etc that are not given in the diagram.  You do not know the durations.  You can not compute EF of activity X.  The only thing you can conclude is: ES of Z = EF of X + 7+1.  Since duration of activity X is not given, we can not compute its EF. 


My answer is : CHOICE 2


Explanation:


If the arrow connecting the 2 activites has no explicit time on the arrow, those two activiyties connected by arrow follow START-FINISH relationship i.e. Activity Z can start after its precedent activity X finishes


Once you explicitly indicate a duration over the arrow, you are putting a mandatory relation of lead/lag between the 2 activities.  Here the 7 days is not a slack/float but a mandatory wait time for activity Z to start after activity X is completed


 


Chandra

manuspmp

Fri, 05/14/2010 - 12:30

Hi,


Can you plz specify that which option is correct among the listed one.....


////manuspmp

The PMP Guru's picture

The PMP Guru

Fri, 05/14/2010 - 13:03

chandra:

Well I guess 7 was the Duration for Activity X and since the Duration was given so I calculate the ES and EF of Activity X assuming this is the First acitivity on the Node as there was no Predecessor for Acitivty X.

 

 

The PMP Guru's picture

The PMP Guru

Fri, 05/14/2010 - 13:10

chandra:

I follow a Professor: Who mentioned this in his video that the one that we see in this diagram is the Duration for Acitivity X.

So I used the same Logic.

Well I guess 7 was the Duration for Activity X and since the Duration was given so I calculate the ES and EF of Activity X assuming this is the First acitivity on the Node as there was no Predecessor for Acitivty X.

 

 

ChandraR

Fri, 05/14/2010 - 13:27

PMP guru,


In my understanding of notations: 


Activity duration is indicated on top of the activity or at the center of the box for the activity;


ES: a small rectangle inside the activity rectangle & top left corner


EF: a small rectangle inside the activity rectangle & to the top RIGHT corner


LS: a small rectangle inside the activity rectangle and to the Bottom left corner


LF: a small rectangle inside the activity rectangle and to the bottom RIGHT corner


Lead/Lag: on the Arrow connecting the activities


Arrow starting and ending: Relationship between activities e.g: FS, FF, SS, SF


Pl. refer PMBOK4, Section 6.2; Figure 6-7 and some other books


 


Chandra

The PMP Guru's picture

The PMP Guru

Fri, 05/14/2010 - 13:33

I am sorry for mis-Leading you Guys.

Chandra is very much right, I think I have to send a Note to the renowed Professor.

Thanks Chandra for correcting me, I just search for an answer in another book and I got it there and as I was going to Apologize, you have already send the Explanation as well.

 

I Apologize...

 

cplusplus

Sun, 05/16/2010 - 21:18

Chandra,


If Choice 4 says:  
Task Z starts 8 days after task X, will it be the right answer?


Also i am too confused i thought: the days that we see in this diagram is the Duration for Acitivity X.


please guys clarify, lot of time they confuse. even though we have the ideas of CPM and slack/float etc.


 


Thank you all.

ChandraR

Mon, 05/17/2010 - 01:48

C++,

Some more explanation on PDM - Your interpreation is correct if  activity Z has a Start-Start relationship with activity X.  In such scenario I expect a 'SS' over the arrow connecting X & Z.  If none of " SS, SF, FF, FS"explicitly stated I assume default FS relationship i.e. Activity Z can only start after Activity X is completed. 

If there is no numerical value is given over the arrow,

ES of activity of Z = EF of preceding activity X + 1

If positive numerical value is given over the arrow, we have a lag and we have to wait that long b4 we start the activity Z

If there is a negative value over the arrow, we have a Lead i.e. we have to start activity Z that many days b4 the preceding activity X completes.

In this case we have to wait for 7 days after completion of X and the earliest we can start Z is the 8th day counting from the completion of X.

What if the arrow direction is reversed?  Activity Z has a FS relationship with activity X. i. e. Actvity Z has to Finish first in order activity X to Start.  So how the arrow head is represented -where it started and where it ended-matters

Chandra

The PMP Guru's picture

The PMP Guru

Mon, 05/17/2010 - 09:25

For Credit to Chandra for even clarifying this Topic to me as well.

Thanks chandra.

Please Check this You tube video and I hope it will be much clearer.

Please I am not promoting anyone in here, Just after this topic was posted, I searched alot to clear my concepts and found this Video to be very useful.

http://www.youtube.com/watch?v=yXj2AEVgs0U

Kind regards,

The PMP Guru

http://thepmpguru.wordpress.com/