Critical path analysis ("CPA") is a widely-used project management tool that uses network analysis to help project managers to handle complex and time-sensitive operations.
Many larger businesses get involved in projects that are complex and involve significant investment and risk. As the complexity and risk increases it becomes even more necessary to identify the relationships between the activities involved and to work out the most efficient way of completing the project.
The essential technique for using CPA is to construct a model of the project that includes the following:
Using this information, CPA calculates:
This process determines which activities are "critical" (i.e., on the longest path) and which have "total float" (i.e. can be delayed without making the project longer).
In project management, a critical path is:
The sequence of project activities which add up to the longest overall duration
The critical path determines the shortest time possible to complete the project.
Any delay of an activity on the critical path directly impacts the planned project completion date (i.e. there is no float on the critical path).
Here is worked example to illustrate how the critical path for a project is determined.
Conventions in drawing the network
The main components of a network analysis are summarised below:
Example network diagram
Consider the following series of activities in a business planning to launch a new product:
Laid out in the correct sequence of activities, the network diagram would look like this before we calculate the EST and LFT for each activity:
The next step is to calculate the EST for each activity.
The EST for task B is 2 months – the time taken to conduct market research (task A)
To calculate the EST for task C, we add the 2 months for task A to the 4 months for designing the product concept (task B) = 6 months
The remaining ESTs can then be added to the network diagram:
The LFTs show the latest time an activity must be completed by to avoid a delay to the project. LFTs are calculated by looking right to left on the network diagram. So:
The main advantages and disadvantages of a business using CPA can be summarised as follows:
Advantages of CPA
Disadvantages of CPA