CPM - Day 0 Method vs. Day 1 Method

Submitted by dlhawe on Fri, 02/15/2013 - 01:42

Does it really matter which method I use to calculate critical path?  Rita and other sources seem to use Day 0 with EF = ES+D, while the PMP PrepCast I am listening to starts projects on Day 1 and uses the formula EF = ES + D -1 (and +1 going backwards)..

Day 0 methods are faster (IMO) to calculate forwards and backwards, while the Day 1 method makes more sense to me when trying to specifically tie activities to a schedule.

So does it really matter?  I'm leaning towards using Day zero but want to make sure I am not missing anything.

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sspawar

Fri, 02/15/2013 - 02:17

You have rightly pointed out, Pros and cons of both methods.

You have better understanding in between these two methods. It is required , because it depends on question asked, how to answer.

Even PMP/PMI - could not firm any one of these two. Perhaps you have seen my blog article dated  Dec 26

at er-sspawar.blogspot.in

----------------------------

Few questions ask ES or LS , and in options they provide answers both based on 0 and 1 method. And thus questions becomes the subject of debate among aspirants. I have faced many such questions/queries in this forum, from good sources - like RITA, Exam Central, Head First etc.

But in other way these are eye opener that aspirants who are following any one of this 2 methods , could know about the other one and their discripencies.

Thats why I posted a permanent article in my blog - er-sspawar.blogspot.in

mohitkum

Fri, 02/15/2013 - 19:41

Does not really matter much as the answer will remain the same e.g.


5 - 3 = 2
4 - 2 = 2


Conceptual understanding is more important.


Thanks & Regards,
Mohit Kumar
 


 

sspawar

Sat, 02/16/2013 - 00:29

 Mr Mohit

You are talking of Float.

I am talking for ES and LS, it matters a lot.

for example from your  quote

If question asks- what is early start of above activity and options given :

A) 5

B) 4

C) 3

D) 2

there are 2 answers , one is as per 0method , second is asper 1 method. and such questions are given in HF, Exam central, RITA, and other books.

It makes confusion, if you are thinking that - no ans will be only as per start one method. it is your individual understanding. 

dlhawe

Sat, 02/16/2013 - 01:02

So given that I am intending to take the test before 5th edition PMBOK goes live, I should answer using day zero calculations?  Sorry to be so dense about this, and I can obviously use both methods, but I wasnt able to find any specifics in PMBOK on what should officially be used.  I would hate to miss a question like this because I was using the wrong method.

sspawar

Sat, 02/16/2013 - 02:24

One Quetion  from E mail

 Hello,

I have a question regarding ES EF LS &  LF questions
you mentioned in the forum that in exam to follow 0 method.
If there are 2 options for 0 and 1 then to go for 0 method.

I want to know  did you get this kind of questions in exam

where both the ans were  present that is 0 and 1 method.
Pls let me know.

Thanks

My answer

No, so far not asked Like such. 
Examiners know better this fact than us.
So Generally you will not find any complexity.
Though in case you find both options without any indication

of which method has to follow then you may prefer 0 start method.

SSP
Sent by BlackBerry®through Vodafone

dlhawe

Sat, 02/16/2013 - 02:25

Day zero it is, thank you all for the clarifications.

dlhawe

Fri, 02/15/2013 - 23:57

Thanks for both of your replies.  I guess the only kind of question where it would really make a difference is if the question asked on what day the critical path ended, but that would be a simple matter of adding up the activity durations.

Thanks again!