How do a schedule work according to a resource's assignment unit?

[Ann]

I have a resource with an assignment unit of 15% and task duration of 4 days.
The problem is that Project is not scheduling the work according to the
resource's assigment units. It shows the finish date 4 days after the start
date, even though the resource is only dedicated to the project 15%.

What am I doing wrong? I've tried task type of fixed duration
effort-driven, fixed duration not effort-driven, fixed units effort driven,
fixed units not effort driven, and fixed work...and I always end up with the
task being finished 4 working days after the start date, even though the
resource would take more like 27 working days to finish this, based on their
assignment units. I am definitely not understanding this correctly!!

 

[David]

Hello Ann,
when you say the task's duration is 4 days, do you mean you would expect the
work required is 32 hours? If so, insert a work column and set work = to the
number of hours expected.
Then as you define the resource's availablility, the duration will change.

 

[Steve House [Project MVP]]

When you make resource assignments, on the initial resource assignment,
Project assumes that whatever percentage you specify for the resource units
is what you had in mind when you came up with the duration estimate in the
first place so it doesn't change the duration. If you subsequently change
the units, then Project will adjust the duration. So if you meant 4 days
for someone @ 100% when you entered 4 days for this task, assign your
resource first at 100% and then edit it to reduce it to 15%. Project will
expand the 4 days duration to about 30 days, 4 days of full-time work when
done at 15%. As you've done it so far, Project is interpreting the way you
made your entries as meaning "this resource will take 4 days when working @
15%."