The critical path method (CPM), is also called critical path analysis (CPA). It can be defined as “the sequence of scheduled project activities that determines the duration of the project”. CPM used in conjunction with the program evaluation and review technique (PERT). It is the lengthiest order of tasks that must be completed on time in order for the project to meet its deadline. Any delay in these activities can delay the completion of the project. Some projects have only one critical path, some projects may have multiple critical paths.
Some Basic Terminology of CPM:
Activity: A task or set of tasks needs to be accomplished within a defined period of time. Activities use resources and time to complete the tasks.
Event: A recognizable state to describe all the things that are happening in a particular situation or resulting from the accomplishment of one or more activities.
Milestones: Recognizable and important events marking substantial progress on the project.
Diagram: A diagram of nodes (a node may represent activities or events) linked by directional arcs that shows relationships among the activities. These are usually drawn w/ a “Start” node on the left and a “Finish” node on the right. Arcs are always tilted w/an point to show the direction of precedence and it is form predecessors to successors.
Path: A series of connected activities between any two events.
Critical path: The set of activities on a path form the project’s start event to its finish. If delayed it will also affect the project completion time.
Critical Time: It is the time required to complete all activities on the critical path.
Step Critical Path Method Planning:
Following are the steps which are required in CPM;
- Define the project and all of its significant activities or tasks.
- Break down the project into various activities systematically.
- Number all the nodes (events) and activities.
- Arrange all the activities in logical sequence.
- Develop the relationships among the activities.
- Decide which activities must precede others.
- Construct the arrow diagram. Draw the network connecting all of the activities.
- Find the time and cost of each activity.
- Identify the critical activities and mark the critical path on the arrow diagram. Compute the longest time path through the network which is called the critical path.
- As the project achieve some tasks then update the CPM diagram.