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How to make MS Project calculate durations correctly with varying resource schedules. RRS feed

  • Question

  • I have used Project for years with Fixed Duration scheduling.

    I now have a project which requires what I believe is Fixed Work scheduling.

    This is a fairly simple project and when applying resources to Fixed Work tasks, the duration is being incorrectly calculated OR the resource is arbitrarily being allocated to strange percentages.

    To illustrate my intent, let me make a very simple project.

    The project has two resources.  One, Alice, has a standard Work Week Calendar.  One, Bob, works 6 days a week, 4 hours a day.

    I create a custom calendar and assign it to Bob in the Resource Sheet

    There are only 2 tasks.

    Task 1 is Start.  It is a milestone with 0 duration.

    Task 2 has Task 1 as its predecessor.  It is set to a Fixed Work task.  It's WORK is 4 hours.  I assign Bob as a resource to this task. 

    ----

    My expectation is the duration of the task will be one day.  Bob has nothing else assigned to him and his work day is 4 hours, thus enabling him to finish a 4hr task in one day.  What is occurring is Bob is automatically getting assigned at only 50% and thus it is taking 2 days.

    Why?


    • Edited by Spektre Thursday, September 24, 2015 9:14 PM
    Thursday, September 24, 2015 9:13 PM

Answers

  • Hmm. That shouldn't happen. However there are a couple of ways around this:

    1. In the Details form reset the Units from 50% to 100% and you're done.
    2. Instead of assigning Bob the way you have, use the Assign Resources dialog (Alt+F10)
    3. In the Assign Resource dialog enter 4h in the Units column for Bob (4 without the h is 4%)
    4. Done!

    Rod Gill
    Author of the one and only Project VBA Book
    www.project-systems.co.nz

    • Marked as answer by Spektre Thursday, October 1, 2015 3:13 PM
    Thursday, September 24, 2015 9:48 PM
    Moderator

All replies

  • Hmm. That shouldn't happen. However there are a couple of ways around this:

    1. In the Details form reset the Units from 50% to 100% and you're done.
    2. Instead of assigning Bob the way you have, use the Assign Resources dialog (Alt+F10)
    3. In the Assign Resource dialog enter 4h in the Units column for Bob (4 without the h is 4%)
    4. Done!

    Rod Gill
    Author of the one and only Project VBA Book
    www.project-systems.co.nz

    • Marked as answer by Spektre Thursday, October 1, 2015 3:13 PM
    Thursday, September 24, 2015 9:48 PM
    Moderator
  • Thank you, this did correct the issue though I wonder why it occurred.

    Scheduling a 3rd task of 16 hrs, correctly created a 4day duration on the Gannt chart.

    Deleting both tasks and reentering the 4 hour task and assigning Bob again allocated him only 50%, strange.

    ---

    As a follow up question.  The spreadsheet durations are incorrect although showing correctly in the Gantt chart.

    For example, for the 4hr task it is listed as 0.5days? and for the 16hr task it is listed as 2days?  after assigning a resource despite there bars in the calendar being correct.  Is this normal behavior?  

    • Edited by Spektre Thursday, September 24, 2015 9:58 PM
    Thursday, September 24, 2015 9:55 PM
  • Hmm. That shouldn't happen. However there are a couple of ways around this:

    1. In the Details form reset the Units from 50% to 100% and you're done.
    2. Instead of assigning Bob the way you have, use the Assign Resources dialog (Alt+F10)
    3. In the Assign Resource dialog enter 4h in the Units column for Bob (4 without the h is 4%)
    4. Done!

    Rod Gill
    Author of the one and only Project VBA Book
    www.project-systems.co.nz

    Trying method 3 was unsuccessful.  Upon trying to enter 4h, Project gives an error box stating, "Project cannot create an assignment with a specific work value on an effort driven task.  Once the assignment is created, you can edit the work value on the assignment."
    Thursday, September 24, 2015 9:59 PM
  • Just guessing, but I think you are trying to input the work rather than estimating the duration and then assigning the resource.

    And maybe misunderstanding the effect of the task type and effort driven settings.

    Try first estimating the duration, then assign the resource at whatever default units and hours MSP wants to, and then use the assign resources dialog box and/or the task usage view to fine tune the work to whatever you want.

    Thursday, September 24, 2015 11:17 PM
  • Yes, I am inputting the work.  This is a fixed work task.  The number of man-hours are known.  The duration is completely unknown until the resource is assigned.

    Estimating the duration first would not be helpful as it would vary greatly depending on which resource was assigned and what that resources work calendar is.

    Misunderstanding is certainly possible, but that is why I am posting here.  It is my belief these are Fixed Work tasks (The number of manhours is known).  Once a task is Fixed Work, it is by definition effort driven.

    Friday, September 25, 2015 1:45 AM
  • I recommend a different approach. Estimate the duration first. Then assign the resource. Allow the resource to be assigned by MSP at whatever the default units are, ie 100% provided max units are 100%, and however it turns out given the resource calendar . Then see if the work matches your work target (it won't). Then adjust the duration until you get the target work.

    Friday, September 25, 2015 3:58 AM
  • I recommend a different approach. Estimate the duration first. Then assign the resource. Allow the resource to be assigned by MSP at whatever the default units are, ie 100% provided max units are 100%, and however it turns out given the resource calendar . Then see if the work matches your work target (it won't). Then adjust the duration until you get the target work.

    This does not work satisfactorily.  Trial and erroring durations to hope you eventually zero in on the correct amount of work on even a 300 tasks project would prove very time consuming.

    Friday, September 25, 2015 1:55 PM
  • Pardon me for bumping in but a couple of things.  I personally work in the Task Entry view (split with the Gantt showing the task form in the lower pane.)

    I followed your steps - Bob works 8:00 am to 12:00 pm Monday through Saturday.

    I create the two tasks changing the duration of task 1 to zero and linking task 1 to task 2.  The duration of task two is the default 1 one - all tasks are autoscheduled, fixed work, effort driven.

    I select task 2 and in the task form select Bob and enter 4 hours of work.  Bob is assigned at 100%, duration is calculated based upon 4/100% and the duration is 1/2 day.  The task finishes at 12:00 pm.

    A day = 8 hours.  The task's duration is 4 hours - or 1/2 day.

    Friday, September 25, 2015 5:40 PM
    Moderator
  • Alternatively, do what Julie says.

    (also, not time consuming and very easy)

    Saturday, September 26, 2015 1:58 AM
  • This seems like a kludge but does fix the allocation problem.
    Thursday, October 1, 2015 3:14 PM