The duration or work value changed unexpectedly when I assigned a resource

Symptoms

When you assign a resource (resources: The people, equipment, and material that are used to complete tasks in a project.) to a task (task: An activity that has a beginning and an end. Project plans are made up of tasks.), the duration (duration: The total span of active working time that is required to complete a task. This is generally the amount of working time from the start to finish of a task, as defined by the project and resource calendar.) or work (work: For tasks, the total labor required to complete a task. For assignments, the amount of work to which a resource is assigned. For resources, the total amount of work to which a resource is assigned for all tasks. Work is different from task duration.) value changes automatically.

Cause

The duration, work, and resource assignments (assignment: A specific resource that is assigned to a particular task.) for a task are interlinked. When you assign a resource to a task, Microsoft Office Project will decrease or increase either the task's duration value or its work value, based on the task type (task type: A characterization of a task based on which aspect of the task is fixed and which aspects are variable. There are three task types: Fixed Units, Fixed Work, and Fixed Duration. The default task type in Project is Fixed Units.).

Task type behavior is described in the following table.

In a If you revise units If you revise duration If you revise work
Fixed units task Duration is recalculated. Work is recalculated. Duration is recalculated.
Fixed work task Duration is recalculated. Units are recalculated. Duration is recalculated.
Fixed duration task Work is recalculated. Work is recalculated. Units are recalculated.

By default, when a new resource is assigned to a task that already has assigned resources and planned work, Project decreases the task's duration. With more work resources contributing to the task, the task should take less time. This is called effort-driven scheduling (effort-driven scheduling: The default method of scheduling in Project; the duration of a task shortens or lengthens as resources are added or removed from a task, while the amount of effort necessary to complete a task remains unchanged.).

When you assign an additional resource to a fixed-duration task (fixed-duration task: A task in which the duration is a fixed value and any changes to the work or the assigned units [that is, resources] don't affect the task's duration. This is calculated as follows: Duration x Units = Work.) that already has assigned resources and that uses effort-driven scheduling, Project adjusts the work values. If a task must take a specified amount of time, and if you add another resource to that task, each resource will be assigned less of the total work.

Resolution

You can change this behavior to more accurately reflect how a particular task is affected when resources are added or removed. For example, you might want to see the total work increasing as you add more people to a particular task, or you might want to change the task type.

Change a task's scheduling options

  1. On the View menu, click Gantt Chart.
  2. Click the task that you want to change.
  3. Click Task Information Button image, and then click the Advanced tab.
  4. In the Task type list, click the task type that you want to change.
  5. If you want to show the increase in total work for the task, clear the Effort driven check box.

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