Why am I getting different values based on order of input when the task type remains the same? RRS feed

  • Question

  • I'm having a hard time understanding the results I'm getting when I input task information. Here are the scenarios with different, unlinked fixed work tasks:

    1. I estimate a task will take 2 hrs to complete and put this into work. If I add 1 resource, work = 2 hrs, duration = 1 day?, Resource A = 25%
    2. On the same task, if I add Resource B (along with keeping A), duration = 0.2 days, Resource A remains 25% and Resource B = 100% (no % shown)
    3. If I try the same scenario (adding first resource, then adding a second) on another task, occasionally it will give a duration of 0.91 days??? What the hell is that about?
    4. If I add 2 hrs for work then add both Resource A and Resource B at the same time I get duration = 0.5 days, Resource A = 25% and Resource B = 100%. Why is it giving a duration of 0.5 days and why does it not adjust the unit % for Resource B?
    5. This one is really blowing my mind. If I don't add work but instead add both resources at the same time first it's either making work 8.2 hrs OR 16 hours! I've gotten this result on the same exact task doing the same exact input. How can this differ?!
    6. No work input, both resources added initially and IF I get the correct 16 hours with 1 day duration, then I go ahead and change work to 2 hours, which produce Resource A & B = 100% and duration = 0.13 days.

    This last scenario is the duration result I want to see so the resources can work on multiple tasks in 1 day, but I typically try to input the work or duration estimates into the schedule and then resources last. I also don't understand how there can be such a wide range of results based on such similar scenarios. Also, having to do it this way creates another step since I have to go back and change the work...although I guess I would be doing that if I input estimates first.

    Can anyone explain why I'm getting those very head scratching differences, as well as provide some insight into how you initially develop a schedule (order of inputs)? I'm wondering if this has something to do with the change in 2010 regarding resources that I still don't understand?

    Tuesday, April 14, 2015 7:47 PM

All replies

  • 1. You told Project how much work BEFORE assigning the resource.  The default task duration is 1 day, so Project did the only thing it could do - calculate resource assignment units.

    2. The task must have been effort driven.  When a task is effort driven and you add another resource, Project assumes the amount of work (2 hours) stays the same.  Project divides the work by the total resources assigned: 20%  (.4 hours) to resource A  and 80% (1.6 hours) to resource B.  Resource B is assigned at his/her max units of 100%.

    3. Is the second task effort driven?  Are you now assigning resources during times when their calendar has non-working time? You haven't given enough to go on for this one.

    4. I'm not seeing that.  I see both resources being assigned to a Fixed Units, Effort Driven task at 25%, each getting one hour of work and a task duration of .5 days.

    5. Again - you're not giving enough to go on.  What is the task duration?  What is your definition of day?  Are you sure you are adding both resources at the same time?  How are you assigning the resources?  Resource Names field in the Gantt chart?  Assign Resources button?  Task Form?

    6. My suggestion is to use the Task Form in the lower part of the window.  If you want a task with each resource working 1 hour, in the task form select the first resource enter 1 hour select the second resource enter 1 hour.  Click OK. 

    The task form allows you to control what happens more more easily than entering data in the table. Consider using a spare text field to input the work estimates.  Then, when you assign the resources, enter the work for each resource.

    I personally:

    • Create the task list including summary and sub tasks as needed.
    • Create the relationships between the tasks using predecessors/successors.
    • Create the resources on the resource sheet including setting accurate max. units.
    • Ask resources for work estimates.
    • Assign the resources to the task entering their work estimates while assigning.

    I hope this helps.

    Tuesday, April 14, 2015 8:28 PM
  • Thank you Julie for the quick reply. As indicated in the first part of my question all these scenarios are dealing with Fixed Work, so yes by default they are effort driven. I should have clarified on the 1st scenario the question mark was just to show duration had not changed, I wasn't actually questioning why it hadn't changed. Scenario 1 worked as expected. Although I don't fully agree with it, Scenario 2 also worked as expected.

    Scenario 3: Yes it is effort driven (fixed work). Resources are just test/fake resources so all information, including calendars, is default. This is one of those cases where I can produce that unusual result only on occasion, not everytime.

    4. In my scenario it's fixed work, but I do get the same result as you with fixed unit. Question still remains in both cases of why is the duration 0.5 days on 2 hours total work? Also, why are both units 25% in fixed units, but in fixed work Resource A is 25% and Resource B is 100% when in both cases they are working 1 hour? Lastly, if Units is going to be changed in this case then why isn't it 13% (1/8 hours)?

    5. This is also fixed work and I'm not touching duration in any of the scenarios. Day is still default at 8 hours. I was assigning resources via Resource Names on the Gantt View. I'm thinking this had to be some sort of glitch because I can't consistently produce the 8.2 hours result, but it happened multiple times.

    I also follow the same steps you do, other than I guess the last one. When you say you enter work estimates while assigning does that mean you do that in the split pane/task details form? I've typically done it from the Gantt View, but that seems to be what's causing my issue because when I tried doing it from task details it is giving me the duration I want. So thank you for that. I still don't understand why there is such a wide range of results, but at least it makes more sense to me that 100% Unit working on a task duration of 0.13 days is 1 hour.

    I apologize for how long this, but I'm trying to get out of some bad habits I've picked up by being forced to develop dumbed down schedules for the past few years.

    Wednesday, April 15, 2015 1:57 PM
  • 4. In my scenario it's fixed work, but I do get the same result as you with fixed unit. Question still remains in both cases of why is the duration 0.5 days on 2 hours total work? Also, why are both units 25% in fixed units, but in fixed work Resource A is 25% and Resource B is 100% when in both cases they are working 1 hour? Lastly, if Units is going to be changed in this case then why isn't it 13% (1/8 hours)?

    Again, sorry I'm not seeing this.  I create a 1-day Fixed Work task and enter two hours of work.  I then assign two resources using either the Task Form or the Resource Names field, I get the same answer: .5 days duration each resource assigned at 25% and with one hour of work.  You lost me on "if Units is going to be changed in this case then why isn't it 13%?"  The assignment units is based upon the 1/2 day duration 1 hour of work for each resource spread over a 4 hour time span.

    To answer your question about entering work - yes I enter in the Task Form for each assignment.  When you enter work in the Gantt view, you are entering work for the TASK.  You can get unexpected results as witnessed by your troubles.

    I have tested the scenarios on both Project 2010 (updated with the latest Public Update) and with Project 2013 (also updated with the latest PU).

    Thursday, April 16, 2015 2:58 PM
  • Well I had some computer issues yesterday when I was wrapping up for the day and lost the test schedules I was using, but I tried that scenario again this morning and can't help but shake my head. Now I'm also getting 25% for both resources. I don't know what the heck was causing those weird results repeatedly. Must be some corrupt code because I didn't do anything differently and it was as basic as it could possibly be: a handful of test tasks and generic resources.

    I still don’t understand why the duration changes to 0.5 days when I first do 2 hours then add two resources. If I use the task information to put in the resources and add 1 hour of work for each I get 0.13 day duration, which is what I would expect. I don't see why it changes duration and units when I go hours first then resources. It's still 2 resources each working 1 hour out of a possible 8 for the day. I understand when you say 25% = 1/4 hours for 0.5 day duration, but in fixed work if I change units (by adding the resources) I thought it would only change duration, not duration and units.

    Friday, April 17, 2015 1:58 PM
  • Where in the Task Information are you entering 1 hour of work? Are you're saying you have a one day, fixed Work task and assign two resources in Task Information.  At that moment you have a 1 day duration task with 16 hours of work (8 hours for each resource).  Then you go and change the work for each resource to 1 hour.  The assignment units stay at 100%, and the duration is calculated to .13 days.  You changed work in a fixed Work task.  Project will recalculate the duration.  You are not "changing units" when you add or subtract resources.  If the task is effort driven (as it is with fixed work), the work will stay the same and duration will increase (remove resources) or decrease (add resources.)
    Friday, April 17, 2015 8:55 PM