The critical path is composed of those tasks whose finish dates affect the finish date of the overall project. In other words, if a critical task finishes late, the project will likely finish late also, unless you are able to adjust to the delay and make up time elsewhere. (Daley, 2011, p48).
Many people misunderstand the term 'Critical Path' assuming that it refers to mission critical project tasks. The Critical Path is the series of tasks that must finish on time for the entire project to finish on schedule. Each task on the critical path is a time critical task. You can also think of it as:
The The best way to understand the Critical path is to see an example. Below is a table showing the precedence of tasks for a simple CD/DVD publishing project
|1. Project start||None||0|
|2. Write contents||1||20|
|3. Produce artwork||1||10|
|4. Design menu||3||5|
|5. Select distribution house||1||5|
|6. Order CDs, cases and inlays||5||1|
|7. Testing and Glass Master||2,4,6||10|
|8. Duping and packaging||7||8|
Mapped out as a precedence diagram we can clearly see the project logic.
This is a simple diagram and you may well be able to spot the critical path already. You may also have noticed that some tasks could be delayed without impacting the critical path i.e. without impacting the end date of Duping and packaging. Most projects are much more complex and the Project Manager will need to follow a process to calculate the critical path and identify the slack in the project. The critical path is Project start - Write contents - Testing and glass master - Duping and packaging.To learn how to create a Precedence Diagram or Work Flow Diagram
Critical path is probably the most useful tools [sic] project management offers for managing resources in a dynamic environment. (Bender, 2009, p42).
Without this technique you will never be truly confident about shortening the duration of your projects or becoming efficient and effective with resources. (Harper-Smith and Derry, 2010, p.194)
In Project Management: Fast Track to Success, Patrick Harper-Smith and Simon Derry explain that understanding the Critical Path can give you a major advantage as a Project Manager. It is only by calculating the Critical Path that the project manager can identify the means by which they can shorten the duration of the project. The only way to reduce the plan duration is to reduce the duration of a task or tasks on the critical path - for example, by adding resources. If the project manager doesn't know the critical path they could easily spend considerable time working to reduce the duration of tasks that will not impact the project end date.
Using Microsoft Project? This video shows how to view the Critical path in MS Project.