TOPIC: Precedence Diagram duration?

I have seen the duration calculated two different ways.

#1) Seems like 0 starting day: LF-LS or EF-ES : Example Rita book
#2) Seems like 1 starting day: LF-LS + 1 or EF-ES + 1 : Example from PrepCast

How do you know which one you should be using? It makes a difference. If LF=15 and LS =8, then the answer for what is the duration could be either 7 or 8 depending on which calculation used.

Start: es 0 =+7 dur = ls 7, next day is es 7 + 7 dur = ls of 14. The zero method does not add a +1 to the next day.

Start: es 1 = 7 dur = ls 7, next day is es 8 + 7 dur = ls 14. The 1 method, you add +1 to the next day.

You have made the assumption that both methods add the +1 to each successive day; that would be incorrect.

Found this link. Not sure why it didn't show up in a search.
www.project-management-prepcast.com/kune...-with-day-0-or-day-1

I should be good. They shouldn't ask such a question it sounds like that would have multiple answers.

The PMP test s loaded with questions that have multiple answers that could be correct. Good Luck.