Critical Path Analysis


    Critical Path Analysis:

    Nature and purpose of critical path analysis

    Network analysis:

    Businesses often have to complete large project, which involves a series of complicated or activities which must be carried out in a certain order. The use of networks helps a business to manage the project effectively.

    It is a vital that a business knows the minimum length of time a project will take to complete. It is also important to know whether a delay in completing individual tasks in an operation will delay the whole project. Network analysis allows a business to find the sequence of tasks which are critical to the project and which, if delayed, will cause delays in the entire operation.  In practice, businesses may use computers to manage large projects, such as the construction of a road system or hospital or manufacturing of a large urgent overseas order for new machinery.

    Before any project starts, it is important that the networks are planned. This involves identifying the tasks that are to take place, how long it will take, and the order in which they will take place. This information may be based on previous experience of project or from research carried out by the business.

    • Arrows and lines show the tasks or activities to be carried out to complete the project
    • Some tasks can be carried out together at the same time
    • Arrows and lines cannot cross
    • Which task takes a certain amount of time
    • Task must be completed in a certain order
    • Circles on the diagram called new show the start and finish of a task or activity
    • There is always a node at the start and end of the project
    • Nodes contain information about the timing involved in the project


    Earliest Start Times:

    The first stage in determining the critical path in the network is to calculate the earliest time at which each of the tasks or activities can start; called the EST (Earliest Start Time). These are shown in the top right of all the nodes.


    Latest Finish Times:

    The latest time a task can be finished without delaying the entire project:

    LFT = LFT at node – time taken to complete previous task

    Identifying the Critical path:

    This shows the projects if delayed will delay the entire project. It is where the EST & LFT in the nodes are the same. But it must also be the route through the nodes which takes the longest time.


    Float: Refers to the amount of time a task can be delayed without causing the project to be delayed.

    • Total Float: LFT of activity – EST of activity – Duration
    • Free Float: EST start of the next task – EST of this task – Duration

    Limitations of critical paths analysis:

    • Information used maybe incorrect
    • Unforeseen events during the project
    • Resources maybe inflexible
    • Very large projects can become extremely complex




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