The difference between how PV is calculated if lag or delay is used in scheduling RRS feed

  • Question

  • When scheduling tasks, it is possible to add lag from the predecessor (which is useful for an amount of time which must pass before the next task (paint drying, for example), or to add delay (task form\schedule\delay).  Delay seems to be useful for adding slack into your project in planning, as it is time that could pass before the next task, but doesn't necessarily have to.

    First - do I have this assessment correct?

    Second - does MSP calculate PV based upon when tasks appear in the schedule regardless of whether they are there due to lag or delay, or do tasks presented with delay assume that they will start straight away, without the delay?

    An aside - the reason that I've been playing with this is because of a bug in the previous version of MSP where an EV graph could not be generated if EV was calculated using physical % complete.  Has this been fixed in MSP 2013?

    Thanks for your help!

    Wednesday, October 29, 2014 6:17 PM

All replies

  • First, the lag (and not delay) in the task form is to be entered in the Predecessors/successors form and not the schedule form. The delay in the schedule form is the delay on an assignment, meaning the delay a resource has on a assignment. And indeed it is not required but just an option given to the scheduler.

    The PV (or BCWS) is calculated based on this formula: timephased baseline costs of the task up to the status date. The lag just implies that the task will occur later in the project, thus the PV will take into account the lag.

    AS per the bug, I couldn't experience it, thus I'll let you or others folks give a feedback on it.

    Hope this helps,

    Guillaume Rouyre, MBA, MVP, P-Seller |

    Wednesday, October 29, 2014 7:02 PM
  • Hi Gryphon003k

    First of all, let's understand what is a lag or lead (or negative lag), ok?

    A lead/lag should only be used for an unchanging period of time that occurs between one activity and another. And a lead/lag should not take resources.

    So, they work perfect to model situations like you metioned (paint drying) and not for introducing delays. The lack of visibility of the lead/lag and the distorcion of the critical path calculation can contribute to schedule risk. So, take care of using leads and lags.

    In terms of Earned Value, see what's happening...

    Just in case, in this example i'm using a % complete earned value method so EV = (% complete)x(baseline cost) and PV is calculated like Guillaume said.




    Alexandre Paiva, PMP, MCTS, ITIL Project Manager +55 (21) 8887-3645

    Saturday, November 1, 2014 10:34 AM