• We have already introduced the concept of critical path analysis and how we can use it to manage projects
• Here we will look at how you use critical path on a hypothetical project where your school is building a new block for Upper Sixth Business Studies students
• The following steps would be involved in drawing the diagram.
1. Identify the tasks involved in the project:
• Obtain permits
• Clear the land
• Pour foundation
• Construct walls and roof
• Install plumbing and electrical systems
• Finish with interior design
• Landscaping
1. Determine the dependencies between tasks:
• Pour foundation can only start once the land is cleared
• Walls and roof can only start once the foundation is poured
• Plumbing and electrical systems can only start once the walls and roof are completed
• Interior design can only start once plumbing and electrical systems are completed
• Landscaping can only start once the building is completed
1. Draw the network diagram:
• Nodes represent each task and are labelled with their names
• Arrows represent the dependencies between tasks
1. Calculate the earliest starting time (EST) and latest finishing time (LFT) for each task:
• EST is the earliest time at which an activity can begin, based on the completion of all preceding activities.
• LFT is the latest time by which an activity must be completed in order to avoid delaying the entire project.

For example:

• Obtain permits: EST 0, LFT 5
• Clear the land: EST 5, LFT 10
• Pour foundation: EST 10, LFT 18
• Construct walls and roof: EST 18, LFT 26
• Install plumbing and electrical systems: EST 26, LFT 32
• Finish with interior design: EST 32, LFT 38
• Landscaping: EST 38, LFT 44
1. Calculate the float for each task:
• Float is the amount of time that an activity can be delayed without delaying the entire project.
• Float is calculated as the difference between the LFT of the next task and the duration of the current task.

For example:

• Obtain permits: float 5
• Clear the land: float 2
• Pour foundation: float 8
• Construct walls and roof: float 6
• Install plumbing and electrical systems: float 6
• Finish with interior design: float 6
• Landscaping: float 0 (no float as it is the last task)
1. Identify the critical path:
• The critical path is the sequence of tasks with zero float.
• In our example, the critical path is: Pour foundation -> Construct walls and roof -> Install plumbing and electrical systems -> Finish with interior design.

By following these steps, we can draw a network diagram and identify the critical path for a project using critical path analysis. This can help project managers allocate resources effectively, reduce the risk of delays and cost overruns, and ensure that the project is completed as planned.