The purpose of a project plan is to maintain control of a project.
As a complicated process, a project always threatens to exceed the limit of your control. Some
people are better than others at controlling complex problems, but all of us reach our limits at some
stage. To maintain control you need help in the form of tools and your best tool is your plan.
The project plan controls the project by:
Breaking a complex process down into a number of simpler components
Providing visibility for obscure or ambiguous tasks in the project
Providing a single point of reference for everyone
Enforcing scrutiny of the sequence and nature of events
Providing a baseline against which execution of the project can be compared
Anticipating likely events and providing pre-planned means of avoiding them
A project plan must be as accurate, complete and as specific as possible. How accurate, complete
and specific of course depends upon how much time and resources you have.