Critical path explained

1 Mar
2013

The Project Management Body of Knowledge (PMBOK) defines the critical path as “the sequence of schedule activities that determines the duration of the project.” Project managers can also apply the critical path methodology technique to “determine the amount of float on various logical network paths in the project schedule network to determine the minimum total project duration.” Critical path explained If you’re just as confused by the PMBOK speak, let me restate it in a way that’s easier to understand. The critical path is simply all the tasks that determine the end date in your project schedule. If one of those tasks is late by one day, then your project end date will be extended by one day. Oftentimes, there will be tasks that are not on the critical path; this is due to the slack in the project schedule. If you refer to your current schedule, you can examine the Gantt chart and quickly identify the tasks that have some float compared to the tasks that have no slack. Slack is the amount of time a task can be delayed without impacting the start date of a subsequent task. The critical path methodology is simply a technique to identify all the tasks that will directly impact the project end date. Figure A depicts a Gantt chart with a set of tasks on the critical path. Figure A Critical path in Microsoft Project In Figure A, there are five tasks in the project schedule and Task 4 is not on the project’s critical path. If Task 1, 2, 3, or 5 is delayed, then the entire project will be delayed. If Task 4 is delayed, it has seven days of free slack before it will start having an impact on the schedule. Since Task 5 is three days in duration, Task 4 could have an actual duration of 10 days before it becomes part of the project’s critical path. If it exceeds 11 days, Task 4 will create a new critical path. Tools are invented for a reason and, fortunately, Microsoft Project can support forecasting, what-if analysis, and detailed scheduling metrics along the critical path. By switching to different views and formatting the Gantt charts, you can quickly identify and monitor the tasks on the project’s critical path. Figure B depicts the free slack in Microsoft Project. All the tasks on the critical path have zero slack in their schedule and that’s why these tasks drive the end date. Task 5 has 7 days of slack and is not included on the critical path. By increasing or decreasing duration on specific tasks, you can see the adjustments in the critical path.

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