Error in Project calculation?

[Jerry]

I am new to Project, and it might be my lack of knowledge, but:

If I have a task (fixed work, effort driven) of 16 hours work, and assign
1 person 100%, MS Project correctly calculates duration of 2 days.
If I add a second person at 100%, duration is (correctly) set to one day.
But if I assign first person 75%, and the other 25%, the duration
is 4 days! Should be 2, shouldn't it? A bug?

 

[Gérard Ducouret]

Hello Jerry,
Project works fine :
- Set the work column for that fixed-work task to 16h.
- Assign the first resource with units = 0,75 or 75%
- Assign the second resource with units = 0,25 or 25%

Never assign a resource withe the 100% default assignment units, expecting
to correct it at 25% for ex. the Duration'll jump !

Hope this helps,

Gérard Ducouret [Project MVP]
PragamaSoft ® - Paris

 

[Jerry]

Hello Gérard,

Thank you very much for the help.

Assigning the resources with proper percentages to start with, does
indeed give correct duration. However, reducing a resource to 75% from
100% is what actually happened to my project in real life, and I
could only get another one for two hours (25%), so that adjustment
had to be made.

Actually it is much more complicated than that. I have a project with
ten people and a list of tasks where the amount of work can be fixed.
There are also others with fixed duration. Some of the 10 people
only work part time. Two are only available for a limited time.
I have to find a way to distribute my resources in the optimal way,
(while respecting all other constraints), and that can only be done through
"playing" with the assignments, e.g. shuffling and increasing/decreasing
some
of them and seeing its effect on the rest.

I "played" for a while like this, and my project which initially lasted
two months, now ends in February 2005!




| Hello Jerry,
| Project works fine :
| - Set the work column for that fixed-work task to 16h.
| - Assign the first resource with units = 0,75 or 75%
| - Assign the second resource with units = 0,25 or 25%
|
| Never assign a resource withe the 100% default assignment units, expecting
| to correct it at 25% for ex. the Duration'll jump !
|
| Hope this helps,
|
| Gérard Ducouret [Project MVP]
| PragamaSoft ® - Paris
|
| "Jerry" <[email protected]> a écrit dans le message de
| | > I am new to Project, and it might be my lack of knowledge, but:
| >
| > If I have a task (fixed work, effort driven) of 16 hours work, and
assign
| > 1 person 100%, MS Project correctly calculates duration of 2 days.
| > If I add a second person at 100%, duration is (correctly) set to one
day.
| > But if I assign first person 75%, and the other 25%, the duration
| > is 4 days! Should be 2, shouldn't it? A bug?
| >
| >
|
|

 

[Sarah]

Jerry,

When you're going to make changes like this to your schedule, I would
suggest that you split the screen and show the Resource Work view of
the Task Form on the bottom part, with the Gantt Chart on the top.
Select the task in the Gantt, then in the bottom you can adjust the
resources individually. If you initially have one resource assigned at
100% for 16 hours, then add another resource without making any other
changes, Project assumes that the two resources will split the work,
so each gets 8 hours. Then you tell Project that the second resource
is only available 25% of the time, so Project schedules that resource
at 2 hours per day. The 8 hours then takes that resource 4 days to
accomplish.

Sarah

 

[Jerry]

Thanks a lot, Sarah

The split view that you suggest is indeed a great way to
work and have the best overview of all parameters. I also
like to add the Work column up in the Gantt part.

I can see the logic applied by Project is indeed the way
you describe. The "fixed work" is fixed also at resource
level rather than only at task level (which is what I expected).





| Jerry,
|
| When you're going to make changes like this to your schedule, I would
| suggest that you split the screen and show the Resource Work view of
| the Task Form on the bottom part, with the Gantt Chart on the top.
| Select the task in the Gantt, then in the bottom you can adjust the
| resources individually. If you initially have one resource assigned at
| 100% for 16 hours, then add another resource without making any other
| changes, Project assumes that the two resources will split the work,
| so each gets 8 hours. Then you tell Project that the second resource
| is only available 25% of the time, so Project schedules that resource
| at 2 hours per day. The 8 hours then takes that resource 4 days to
| accomplish.
|
| Sarah
|
| > | "Jerry" <[email protected]> a écrit dans le message de
| > | | > | > I am new to Project, and it might be my lack of knowledge, but:
| > | >
| > | > If I have a task (fixed work, effort driven) of 16 hours work, and
| > assign
| > | > 1 person 100%, MS Project correctly calculates duration of 2 days.
| > | > If I add a second person at 100%, duration is (correctly) set to one
| > day.
| > | > But if I assign first person 75%, and the other 25%, the duration
| > | > is 4 days! Should be 2, shouldn't it? A bug?