• 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.

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