A project plan that contains only tasks can adequately support the scope of your project. You need only make sure that your plan includes all the tasks required to accomplish your goals. But if you want to exercise fine control of your project both at the project level and at the task level, you should assign resources to tasks.
At the project level, you can add or remove resources to bring them into balance with scope and time at any phase of your project. For example, if you add a new feature to your product, thus increasing the project scope, you can add more resources. Or, if your deadline is delayed by several months, you can compensate for downtime by removing resources from your project and adding resources to a more urgent one.
At the task level, you can fine-tune the trio of work, duration, and resources to schedule each task at the right time, make each task as short as possible, and use resources efficiently. For example, if a task duration pushes the project
end date beyond your deadline, you can either assign more resources to the task or lengthen the work hours of assigned resources. Or, if one person has too much work and another too little, you can assign one person to spend less time on tasks and the other person more time.
If your project has only a few tasks requiring few resources, and you don’t need to track costs in detail, you might not need to assign resources to tasks. If you don’t assign resources, you can still track task progress and some costs, but Microsoft Project won’t be able to calculate resource costs as the project progresses. You’d have to enter any updated resource costs yourself.
When you do assign resources to tasks, you gain several benefits:
The way Microsoft Project uses work, duration, and resources to schedule tasks is a process called effort- driven scheduling, which is the default scheduling method. With effort-driven scheduling, you can see immediately the effect of assigning a resource to or removing a resource from a task.
You can manage your resources by controlling when a resource starts working on a task and by removing resources that are no longer needed.