The relationship between time, scope, and cost is called the project triangle. The relationship between duration, work, and units can aptly be described as Project’s Bermuda Triangle. Plenty of project managers enter this part of Project and are never heard from or seen again. When we interviewed project managers who had given up on previous versions of Project, a common theme emerged: they had no trouble building their project file until they started assigning resources to tasks and changing resource assignments during the course of the project.
Difficulties with setting task type and resource assignment mushroomed when project development started and task duration or work changed in what seemed to be unpredictably ways. In this section, we’ll demystify duration, work, and units by examining how and when Project calculates each of the three values. When you understand how Project calculates and recalculates, you can set task types and assign resources confidently, knowing that Project will behave as you intend it to as you move into project implementation. Project 2000 uses the same calculation methods as earlier versions of Project. If you’re an experienced Microsoft Project user and understand task types and effort-riven scheduling, you can skim or skip this section. But if you’re new to Microsoft Project, or if you’re one of ~ many project managers who’ve been lost in the Bermuda Triangle, read on. We
wrote this section for you.
There a three tables of data used in Project 2000: tasks, resources, and assignments (relationships between tasks and resources). When you assign resources to tasks, Project takes the task’s duration (which may bean estimated duration) and multiplies it by the specific percentage or number of units of the resource to arrive at the hours of work that will be done in the task .
The relationship between duration, units, and work is an assignment version of the project triangle, as shown in Figure 10.l.
• Work is the assignment version of project scope. Work defines what will be accomplished in the assignment: sixteen hours of painting, four hours of shipping, five days of training, and so on.
• Assigning units of employees or machinery to a task incurs cost.
• Duration is time on the project timeline: nothing more, nothing less. The terms are different, but the concept is the same. Just as a change in scope after the project is underway requires the project manager to adjust the budget or timeline, a change in work forces Project 2000 to recalculate units or duration.
Duration is chronological: the amount of calendar or clock time that will pass between the beginning and end of the task. Changes in duration affect the schedule. If a task’s duration is supposed to be one day and it takes three; dependent tasks will have to start
two days later than scheduled.
Three people start 011 a Web design task at the beginning of the day. One person “leaves halfWay through tile day, but is replaced by another person. The task is completed it at the end or the eight-hour workday. The task’s duration is one day. Work is the number of personhours or machine-hours spent on a task. 111e three people work a total of twenty four hours in their eight-hour day. Units are the resources committed to the task and are usually expressed as a percentage (although you can change this setting to use numbers) TIle task “used” 100% of two resource units, Amy Ben, 200%) and 50% of two resource units, Carol and Dennis, (100%), for total Web design resource units of 3OOOAl. Here’s what this task looks like in the Gantt Chart’s Entry table: Duration, work, and units are interdependent, because work is duration multiplied by units: W=D*U. If the two part-time workers hadn’t been assigned to the task (leaving only ‘:00% units), one of two things would have to be different:
• The task duration would be longer (2 days rather than I).
• Less work would be invested in the completed Web design (16 hours rather than 24). If the total hours of Web design work required were 48 hours instead of 24, either of the following would happen:
• It would take 2 days (duration to finish the design. _ OR
• 6 units would be assigned to finish the task in one day.
If we had to get the job done in half the time (duration of a ,half day), either of the following would happen;
• Less work would be done.
• The units would be increased to 600%. It isn’t always possible to complete a task with less work, to assign more units, or to spend more days or hours completing the task. In just a few pages, you’ll see how to change task settings to let Project know which values to calculate and which to leave alone. But first, we’ll see how work, duration, and resource units Interact when you . make an assignment with Project 2000’s default task settings .
If you want to see work, duration, and resources in one view, there are two ways to do it: with the Task Form or by inserting columns in a view. Like the Task Information dialog box, the Task Form displays information about one task,
The Task Form can be displayed along with a view such as the Gantt Chart view, and is the best place to set complex assignment information like resource delay. It’s’ also the view many project managers choose when they change task settings as they assign resources to tasks. We’ll return to the Task Form later in this chapter when we need that level of detail. For simple resource assignment, however, we find that it is a lot easier to see how Project 2000 calculates work when we use the familiar Gantt Chart view with an Entry table, modified to include a Work column. With the addition of the Assign Resource dialog box, we can see resources, duration, and work. Our Project work space looks like when we’re getting ready to assign resources. To set up the Project 2000 work space, as shown in Figure 10.3, follow these steps:
1. Choose View> Gantt Chart to display the Gantt Chart.
2. Choose Views> Table> Entry to display the Entry table in the Tasks area.
3. Adjust the vertical split bar to display the Duration and Start Date columns.
4. Right-click on the Duration column and choose Insert Column from the shortcut menu.
5. Select Work from the Field Name drop-down list, and then click OK.
6. Click the Assign Resources button on the standard toolbar, or choose Tools :> Resources >Assign Resources from the menu to display the Assign Resources dialog box.
TO examine the way Project calculates duration, work, or units when you assign resources, we created a small project file. Our project has ten tasks with two-day duration (Task 1, Task 2, etc.) and five resources: Amy, Ben, Carol, and Dennis, who have specialized roles; and a pool of non-specialized workers, as shown in Figure lO A.
Each task has an estimated duration, but both work and units (resources) are zero because no resources have been assigned. If you take a couple of minutes and create this simple project, you can play along. Oust sit the book down. We’ll watt.)
For calculation purposes in Project, a day is 8 hours unless you previously changed the Hours Per Day Calendar option). If Amy spends ‘100% of her time for two days working on Task 1, she’ll be working 16 hours: 1 unit x 2 days x 8 hours per day = 16 hours
of work. To assign a resource to a task:
1. Open the Gantt Chart (View Gantt Chart) and Assign Resource dialog box (click the Assign Resources toolbar button).
2. In the Entry table, select the task (or tasks) for which you want to make the assignment.
3. In the Assign Resources dialog box, select the resource (or resources) you want to assign.
4. Click the Assign button,Now, assign two resources, Ben and Carol, to Task 2. Project calculates that two people assigned for two days will complete 32 hours of work (2 units x 2 days x 8 hours per day):
Using Project to Calculate Required Resources
In Tasks 1 and 2, we knew how many people we could assign (units) and the number of days we could assign them (duration). Project calculated the remaining variable, work, by multiplying units by duration.
Task 3 is different. This task includes 64 hours of work that need to be completed. We don’t want Project to calculate work as it did 111 the first two tasks: we know how much work needs to be done. We need to know how many resources are required or how long the task will take with the resources we assign.
When you enter a value for work before assignable resources, Project calculates the units required to complete the work within the duration: When we select the Workers resource and click the Assign button, Project divides the work (64 hours) by the duration (2 days), and determines that 4 units of resource (400%) are required to complete the work within the duration:
What if we have only three workers available for Task 3? If we reduce the Units available to 300% by using the spin box control or typing a new percentage in the units field of the Assign Resources dialog box; Project adjusts the task duration rather than the work. The Resource Name at the right end of the task’s Gantt Chart bar now reads [300%). The three workers can complete Task 3, but it will take them more time: