In the illustration above, two tasks have a relationship. Task A is the predecessor task, and Task B is the successor task. Both of these tasks are considered to be non-critical because they both have flexibility. Let’s focus on Task A. EA marks the earliest possible time Task A can start. SS marks the scheduled start time for Task A. By default, all tasks are scheduled to start at the earliest possible time, unless you specify otherwise. In the example above, Task A is scheduled to start later and therefore has been delayed. SE marks the scheduled end time for Task A, and LE marks the latest possible time Task A can end. Both of these tasks have slack, the amount of time a task can slip before it affects another task’s dates or the project finish date. Free slack is the amount of time Task A can be delayed before affecting the start time of Task B, and total slack is the amount of time that Task A can be delayed before affecting the finish date of the project. The summary task summarizes Tasks A and B.
Critical tasks, not shown above, have no slack; therefore, delaying this type of task would mean delaying the project. A critical path is a series of critical tasks. All tasks on a critical path must be completed on time for the project to finish on time. If one task on a critical path is delayed, then the project is delayed. In Microsoft Project, a critical path is shown on the Gantt chart and the Network Diagram Chart in red. |
