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them. Once a task is assigned, the team member who is performing it is not available for
other tasks until the assigned task is completed. While some tasks can be assigned to any
team member, most can be performed only by certain people. If those people are not
available, the task must wait.
Some tasks may require more than one person to be assigned to them—for example, a
programming task may require three programmers. In this case, the effort for the task
should be divided among those resources. The project manager must keep in mind the dif-
ference between effort and duration. Duration is the amount of time that elapses between
the time the task is started and the time it is completed, measured in hours (or days,
weeks, etc.). It does not take into account the number of people performing the task.
Effort is measured in person-hours (or person-days, person-weeks, etc.), and represents the
total number of hours that each person spent working on the task. For example, if 3 peo-
ple worked on a task together for a total of 2 working days, the duration required to com-
plete the task was 16 hours (at 8 hours per day, with only 5 or 6 of those hours actually
devoted to software engineering work). However, since each of the 3 people spent 16
hours on the task, the total effort required was 48 person-hours (keep in mind that some
tasks are not divided evenly between resources; the total effort should reflect the actual
time worked per resource).

It’s possible to allocate one resource to two tasks simultaneously by assigning a percentage
of the resource’s time to each task. When the task stretches over several days, but the
resource is needed only for part of each day or a few days of the task, that resource can be
assigned part-time to the task. For example, a resource can be 50% allocated to two tasks,
or 30% allocated to one task and 70% to another, etc.

In cases where more than one person is allocated to a task, the project manager must take
overhead into account. Overhead is any effort that does not go to the core activities of the
task but is still required in order for the people to perform it—a sort of “real world” cost of
actually doing the work. For example, 2 people performing a task will require more effort
than 1 person doing the same task: if the duration of a task is 12 days, it may require 7
days for 2 people to finish it, because they need an additional day to compare and inte-
grate their work. The trade-off is that, while assigning two people to the task requires

more effort, the task has a shorter duration.
One useful way to compensate for the extra overhead is to use the range that was gener-
ated by the Wideband Delphi estimate (which was for effort, not duration). The project
manager can choose an effort estimate from the low end of the range if fewer resources
are allocated to the task, whereas an estimate from the higher end can be used for a larger
number of resources. The estimation team may have also made assumptions about the
number of resources required to perform the task.
It is important to remember that resources are individual people, and no two people will
take exactly the same amount of time to perform a task. The project manager should be
familiar with the relative expertise of each team member. A senior programmer can often
do a job in a fraction of the time that it would take a junior programmer to do the same

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