Critical path

In project management, a critical path is the sequence of project network terminal elements with the longest overall duration, determining the shortest time to complete the project. The Gantt chart invented by Henry L. Gantt during World War I lists each task in sequence of their beginning time with a graphic showing how long each will take. In the 1950s two techniques built on the Gantt method: critical path method (CPM) and performance evaluation and review technique (PERT). The purpose of PERT is to find the schedule through all the tasks that would take the least time to accomplish the job, while CPM would also find that with the lowest cost. PERT also allows the introduction of probabilistic elements. If used properly, the duration of the critical path determines the duration of the entire project. Any delay of a terminal element on the critical path directly impacts the planned project completion date (i.e. there is no float on the critical path). A project can have several, parallel critical paths. An additional parallel path through the network of tasks with the total durations just shorter than the critical path is called a sub-critical path. Originally, the critical path method considered only logical dependencies among terminal elements. A related concept is the critical chain, which adds resource dependencies. The critical path method (CPM) was invented by the DuPont corporation during the 1950s. Its application in the US Navy included asking each person responsible for a specific task in the network of tasks, how long a particular task would take, rather than a third-party estimate. It was believed that this improved management efficiency.