There are three variables which affect the each task in project plan. They are Work, Duration and Units.
Work is the amount of effort, measured in time units (like hours or days), that a resource needs to complete the task. The total work for a task is the sum of all those time units, no matter how many resources are assigned to the task.
Duration is the length of working time between the start and finish of a task. Project bases the calculation of a task's duration on the amount of work and the amount of resource units assigned to it. The working time for a task is defined by the project calendar, resource calendar, task calendar, or any custom calendars you set for a project.
Resource Units indicate how much of a resource's available time, according to the resource calendar, is being used to work on a particular task. Resources are the people, equipment, or other materials that are applied to completing a task. In a project schedule, resource effort is expressed as assignment units or sometimes just as units.
Project is constantly working to keep the following equation in balance on task:
Work = Duration * Units
Microsoft Office Project 2003 uses one of three task types to calculate the duration of tasks and subsequently their finish dates.
- Fixed Units
- Fixed Work
- Fixed Duration
The task type determines how project goes about keeping it in balance. It is dependant on one of the 3 components being fixed.
In your project plan, one of the below three variables always be “Fixed”, which means it can not be changed when the other two variables change. There are three settings on the Task Type can be define on task.
How to define task type:
- On the View menu, click Gantt Chart
- In the Task Name field, select the task whose task type you want to change
- Click Task Information, and then click the Advanced tab
- In the Task type box, click the task type you want to set
If you click Fixed Work in the Task type box, you cannot change the Effort driven setting for the task.
You can view and change the task type for each task directly in your view by inserting the Type column.