Microsoft Project 2010 : Fine-Tuning Task Details (part 5) - Changing Task Types

2/11/2014 1:15:40 AM

5. Changing Task Types

That Project uses the following formula, called the scheduling formula, to calculate a task’s work value:

Work = Duration × Assignment Units

where assignment units are normally expressed as a percentage. Remember also that a task has work when it has at least one work resource (people or equipment) assigned to it. Each value in the scheduling formula corresponds to a task type. A task type determines which of the three scheduling formula values remains fixed if the other two values change.

The default task type is fixed units: If you change a task’s duration, Project will recalculate work. Likewise, if you change a task’s work, Project will recalculate the duration. In either case, the units value is not affected.

The two other task types are fixed duration and fixed work. For these task types, Project uses a timephased field called peak units when responding to schedule changes.

For a fixed-work task:

You can change the assignment units value and Project will recalculate the duration.
You can change the duration value and Project will recalculate peak units per time period. The assignment units value is not affected.

Note

You cannot turn off effort-driven scheduling for a fixed-work task.

For a fixed-duration task:

You can change the assignment units value and Project will recalculate work.
You can change the work value and Project will recalculate peak units per time period. The assignment units value is not affected.

Project also keeps track of the highest peak units value per assignment. This value is stored in the Peak field, which you’ll work with in the sidebar.

In previous versions of Project, it was possible (in fact, it is likely) that a resource’s initial assignment units value would change, and this led to unexpected results with regard to the scheduling formula. This behavior has changed in Project 2010. Project now tracks both the assignment units value and a calculated value called peak (or, when viewed on a timescale, peak units).

Project uses the assignment units value when initially scheduling or later rescheduling a task, but it uses peak units when reporting a resource’s maximum peak units value. Here’s one example. If you initially assigned a resource at 100% assignment units to a 1-day, fixed-unit task, Project used that value to initially calculate 8 hours of work. However if you then recorded 10 hours of actual work on the task, previous versions of Project would have recalculated the assignment units to be 120% to keep the scheduling formula accurate. If you then added more work or changed the duration of the task, Project would have scheduled the task using the 120% assignment units value—probably not the result you’d want. Project 2010, however, will record the 120% peak value, and if you later add work or change the duration of the task, Project will use the original assignment units value of 100% rather than the peak value of 120% to reschedule the task.

Which is the right task type to apply to each of your tasks? It depends on how you want Project to schedule that task. The following table summarizes the effects of changing any value for any task type. You read it like a multiplication table.

Assignment Units, Peak, Peak Units, and the Scheduling Formula

Note

You cannot change the task type of a manually scheduled task, and the effect of the task type on the scheduling of a task as described here applies only to automatically scheduled tasks.

To view the task type of the selected task, on the Task tab, in the Properties group, click Information. Then, in the Task Information dialog box, click the Advanced tab. You can also view the task type in the Task Form. (When in the Gantt Chart view, you can display the Task Form by clicking Details on the View tab, in the Split View group.) You can change a task type at any time. Note that characterizing a task type as fixed does not mean that its duration, assignment units, or work values are unchangeable. You can change any value for any task type.

In this exercise, you change a task type and some scheduling formula values.

On the View tab, in the Task Views group, click Task Usage.

The Task Usage view appears.
In the Task Name column, select the name of task 8, Copyedit.
On the Task tab, in the Editing group, click Scroll to Task.

Tip

To select a task quickly, even a task you can’t see in the current view, press Ctrl+G and in the ID field of the Go To dialog box, enter a task number, and then click OK.

Project displays the details for task 8, Copyedit, and its assignment.

The Task Usage view groups the assigned resources below each task and shows you, among other things, each task’s duration and work—two of the three variables of the scheduling formula.
If necessary, drag the vertical divider bar to the right so that the Finish column is visible.

Next, you’ll add two columns to the Task Usage view so that you can see the assignment units (the third variable of the scheduling formula) and the peak values. You don’t need to modify this view every time you want to use it, but for our purposes here, this is a good way to illustrate the effect of changing task types and scheduling formula values.
Click the Start column heading, and then, on the Format tab, in the Columns group, click Insert Column.

A list of fields appears.
Click Assignment Units.
Click the Start column heading, and then, on the Format tab, in the Columns group, click Insert Column.
Click Peak.

Project inserts the Assignment Units and Peak columns to the left of the Start column. Peak is the resource’s maximum units value at any time throughout the assignment’s duration.

You can see that task 8 has a total work value of 240 hours, a resource assignment units value of 200%, and a duration of 15 days. Next, you will change the task’s duration to observe the effects on the other values.

After a discussion between the two copyeditors about who will perform the copy-edit, you all agree that the task’s duration should increase and the resource’s daily work on the task should decrease correspondingly.
In the Duration field for task 8, type or select 20d, and press the Enter key.

Project changes the duration of task 8 to 20 days and increases the work to 320 hours. Note that the change highlighting applied to the Work and Duration values. You increased the duration and wanted the total work to remain the same (it didn’t), so you will use the Action button to adjust the results of the new task duration.
Point at task 8’s Duration field, and then click the Action button.

Review the options on the list that appears.

Because task 8’s task type is fixed units (the default task type), the Action’s default selection is to increase work as the duration increases. However, you’d like to keep the work value the same and decrease assignment units for the task’s new duration.
On the Actions list, click Resources will work fewer hours per day so that the task will take longer.

The assignment units value decreases to 150%, and the total work on the task remains unchanged at 240 hours.

Next, you will change a task type and then adjust the work on the task.
In the Task Name column, select the name of task 24, Final review.
On the Task tab, in the Editing group, click Scroll to Task.

Project displays work values for task 24, Final review in the timephased grid.
On the Task tab, in the Properties group, click Information.

The Task Information dialog box appears.
Click the Advanced tab.

The selected task describes the final review of the new book’s page proofs. As you can see in the Task Type box, this task has the default task type of fixed-units. The task is scheduled for five days. You will make this a fixed-duration task.
In the Task Type box, select Fixed Duration.
Click OK to close the Task Information dialog box.

Next, you’ll add work to the task.
In the Work field for task 24, Final review, type 150h, and then press Enter.

Because this is a fixed-duration task and you’ve added work, Project adjusted the peak value to 125%; this represents an intentional overallocation. On the right side of the usage view, you can see that the resources assigned to task 24 now have 10 hours of work scheduled per day. Their original assignment units values of 100% each remain unaffected, however.

Many people misunderstand task types and effort-driven scheduling and conclude that these two issues are more closely related than they really are. Both settings can affect your schedule. Whereas the effect of a task type applies whenever you edit a task’s work, duration, or unit values, effort-driven scheduling affects your schedule only when you’re assigning or removing resources from tasks.