Assuming you are currently looking at a task that is 3 hours in duration and
3 hours of work with a resource assigned at 100%... change the task to be
fixed work and then change the duration to be 3 days.
This behavior is dependent upon the method that you used to make the
assignments and on the task type. If you first create a task, set the task
level work equal to 3 hrs, set the task level duration equal to 3 days and
then assign the resource without entering any units or work at the resource
level then you would have gotten the result that you wanted regardless of the
task type (fixed duration, fixed units, fixed work) and regardless of whether
it was effort driven.
If you follow the above approach but are assigning more than one person,
then you do need to understand whether you want two resources working 1 hour
each for three days or two resources working 1/2 hour each for three days or
2 resources working 1 hour each for 1.5 days. The result is based on the
task type and effort driven settings. You can reference the MS Project help
for a good description of the different types and the results.
Finally, if you had first set the task as 3 days of duration and then at the
point of the assignment, set the assignment work equal to 3 hours...then you
would have wanted to set the task as fixed duration first (note that the
effort driven indicator only makes a difference if assigning more than one
resource).
Long answer to a short question...sorry.
John