Critical Path Methodology (CPM)

The critical path is the sequence of activities whose sum of activity time is longer than that for any other path through the network
Critical Path Analysis is commonly used with all forms of projects, including construction, aerospace and defense, software development, research projects, product development, engineering, and plant maintenance.
Any project with interdependent activities can apply this method of mathematical analysis.
All project schedules have (at least) one critical path, usually only one in non-manipulated project schedules.
The critical path is important because if everything goes according to the schedule, their duration gives the shortest possible completion time for the overall project
Activities that are not in the critical path have slack time
Slack time – It is defined as the amount of time a task can be delayed without causing another task to be delayed or impacting the completion date of the overall project.
Activities on a critical path have zero slack time, and conversely, activities with zero slack time are on a critical path
When planning to add personnel to tasks imposing time constraints on the duration of a project, the project’s critical path should be revalidated first.
Here is a simple example of Critical path methodology:
The above picture represents a project. Let us say Project A. The stages of the project range from Stage 1 to Stage 11. There are different ways to complete the project, i.e., to reach stage 11. The numbers mentioned above the arrow marks represent the time taken to complete each task. Now, let’s calculate the time taken to complete the project’s task and the different ways to complete the project.
Path 1 = Stage 1 – 2 – 5 – 7 – Stage 11 = 3 + 2 + 3 + 7 = 15
Path 2 = Stage 1 – 3 – 4 – 6 – Stage 11 = 1 + 5 + 3 + 5 = 14
Path 3 = Stage 1 – 8 – 9 – 10 – Stage 11 = 7 + 3 + 2 + 1 = 13
Path 4 = Stage 1 – 3 – 4 – 9 – 10 – Stage 11 = 1 + 5 + 1 + 2 + 1 = 10
Now, the critical path is the longest route in completing the project. In such a case, in the above picture, path 1 is the longest route, which takes the maximum time to complete the project.

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