Calculating Actual Duration for a given Actual Work RRS feed

  • Question

  • Hello,

    Can anybody please  explain why Project doesn't calculate Actual Duration for a given Actual Work by using driver resource (longest) duration  as it does for calculation of total task's Duration for a given total task's Work.

    For example, suppose we have a  36h, 3d fixed unit task with 2 resources R1(100%) and  R1(50%). 

    Project calculates task's Duration as the longest duration required by it's driver resource to complete the task. As Work = Duration * Units, the Duration calculated for each resource will be as follows:

    Duration (for R1) = Work (R1) / Units (R1) = 24h/100% /8h=3d

    Duration (for R2) = Work (R2) / Units (R2) = 12h/50% /8h=3d

    So in this case both resources are drivers, so 3d is the task's Duration.

    (In this case the same result would be achieved by calculating Duration = Total  Work / Total Units = 36h * 150% = 3d)

    Now lets add  some Actual Work for resource R1:

    As R1 was the only resource that performed  Actual Work of 10h,   by analogy with calculations above, I expected that task's Actual Duration could have been calculated as :  Actual Duration =  Actual Work (R1) / Units (R1) = 10h/100% /8h=1.25h

    But Project thought differently.  It used the Total Actual Work and Total Units for   calculations of the Actual Duration  :

    Actual Duration = Total  Actual Work / Total Units = 10h / (100% + 50%) = 10h/150% = 0.83h

    Please explain why the driver resource approach in calculation the Actual Duration doesn't work?

    Thank you,


    • Edited by Alex Shafir Monday, August 15, 2016 9:33 PM
    Monday, August 15, 2016 9:32 PM