View source for Scheduling: Critical path, PERT, Gantt

=== HISTORICAL BACKGROUND ===
The US Navy developed the management tool PERT in the 1950’s. It was developed with the purpose of assisting the Polaris Project and the idea was to develop a management tool to handle the contractors on the project. The Navy was worried about the threats from the Soviet Union and they wanted to deliver the project as quickly as possible. PERT was a part of the reason why Polaris finished ahead of schedule and on budget.<ref> John Ryding Olsson et. al., '''Power in Projects, Programs and Portfolios''', 2015.</ref> <ref> Archibald, R. D. (1987), "The history of modern project management. Key milestones in the early PERT/CPM/PDM days: how did we get here—where do we go?", Project Management Journal, 18(4), 29–31 </ref><ref> https://www.smartsheet.com/pert-101-charts-analysis-and-templates-more-accurate-project-time-estimates </ref>
Approximately at the same time as the PERT tool was developed, DuPont developed the Critical Path Method (history of….). It was created with the intention to handle similar challenges in a planning process of chemical plants. The critical path is a sequence of events in any projects that has a direct impact on the duration of the project. If any of these activities are delayed, it will delay the entire project. The tools PERT and critical path method/analysis are complementary tools since they both address the longest duration time of a project.