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Unformatted text preview: this path falls behind schedule, the end
date for the project will slip accordingly.
Some of the tasks in Figure 6-3 have the same EF and LF times, as well as the same ES and LS times. These
tasks are on the critical path. In the figure, they are shown with bold outlines to indicate exactly where the
critical path lies.
Critical path activities have no latitude. They must be completed as scheduled or the entire project will take
longer than the allotted 165 minutes. Knowing where the critical path is tells a manager on which areas to
focus; the other tasks have latitude, or float. This does not mean that they can be ignored, but they have less
chance of delaying the project if they encounter problems. The Edge Sidewalk task, for example, has an ES
time of fifteen minutes and a LS time of seventy-five. The difference between the two is sixty minutes, which
is the float for the task. What good is the float? Well, we know we can start the task as late as seventy-five
minutes into the job and still finish the project on time. If your son is doing this task, he can watch a
sixty-minute television program during that time and still get his Edging task done on time.
Remember, too, that the times are all estimates. This means that tasks may take more or less time than we
have scheduled. So long as they do not take longer than the scheduled time plus the available float time, the
job can be done on time. Critical tasks, which have no float, must be managed in such a way that they take the
scheduled time. This is usually done by adjusting the resources (effort) applied, either by assigning more
resources or working overtime (increasing resources in either case).
It is bad practice to schedule a project so that overtime is required to meet the schedule, since if problems
are encountered, it may not be possible to work more overtime to solve them.
Adjusting the resources is not always possible. Applying overtime often increases errors, leading to rework,
which may mean that you don’t get the job done any faster than if you had simply worked a normal schedule.
Further, there is always a point of diminishing returns when you add bodies to a task. At some point the
workers just get in one another’s way, actually slowing work down rather than speeding it. Overtime should
be kept in reserve in case it is needed to resolve problems, and it is never a good idea to schedule a project so
that overtime needs to be worked just to meet the original schedule.
Another point of great importance: all members of the project team should be encouraged to keep float times
in reserve as insurance against bad estimates or unforeseen problems. People tend to wait until the latest
possible start time to begin tasks; then, when problems occur, there is no float left and they wind up missing
the end date. When a task takes longer than originally planned, it can impact the end date for the entire
project, since once a task runs out of float, it becomes part of the critical path. In fa...
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This document was uploaded on 09/27/2013.
- Fall '13