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Critical Path Analysis and PERT Charts

CMS Vocational Training Hadyn Luke posted this on Friday 10th of December 2021 Hadyn Luke 10/12/2021


Critical Path Analysis and PERT Charts

If you’re running a project of any kind, Critical Path Analysis and PERT Charts can help you keep on track and meet your deadlines.

You can use these frameworks to map out how long it will take you to carry out the activities involved at each stage of the project and to identify and manage the tasks that are crucial to completing the project on time.

What is Critical Path Analysis?

The Critical Path Method (CPM) is a visual representation of the tasks involved in a project in order to establish a critical path of activities. It breaks each stage down into a separate part with an estimated time for completion, from shortest to longest.

These are displayed on a flow chart to provide a step-by-step approach and keep a project on track.

Critical Path Analysis is the process of studying the chart to work out the key activities most likely to delay the project if they are not completed in time. It encourages you to think about and prepare for any internal or external factors that could throw the project off course.

What are PERT Charts?

PERT stand for Program Evaluation Review Technique. PERT Charts are used to work out the time required to carry out a project, plan each task involved and review the project as you go along.

How to create a PERT Chart and use Critical Path Analysis

The process of creating a PERT Chart is as follows:

  1. Identify the key tasks you need to carry out; focus on the main activities only and create an outline using a list, table or tree structure
  • Work out how long each task is likely to take; you may find it useful to list the best case scenario, the worst case scenario and the most likely estimate
  • Work out the order they need to happen; establish which activities are dependent on others to take place
  • Create a PERT Chart or Network Diagram to illustrate the various activities and map out their time frames – there are software programmes available online to help you with this
  • Work out the critical path by looking at the longest sequence of activities in days and/or by identifying the earliest and latest start and end times for each task; note that there may be more than one critical path in a complex project
  • Keep updating the PERT Chart as the project progresses; reassess the critical path if required

What’s the difference between Critical Path Analysis and PERT Charts?

The key difference relates to the way you will work out how long it will take to carry out an activity. With Critical Path Analysis, this timeframe is estimated as a best guess, while a PERT Chart will focus on the most realistic completion time.

Why use CPA and PERT Charts?

The use of CPA and PERT Charts makes it easier to plan each activity that needs to happen within a project and identify the most important tasks.

As well as working out the time that each task will take, planning is likely to include:

  • Identifying who will be responsible for each element of the activity
  • Ensuring staff have the skills, experience and time to carry out the activity
  • Ordering materials and equipment
  • Contacting and liaising with outside partners who are contributing to the project
  • Identifying anything that could delay each specific task, from staff holidays to product delivery delays

CPA and PERT Charts are often employed in tandem, so that you can establish the best way to schedule a project, easily view the steps on a visual chart and review the process as you go along. You’ll be able to see which steps are most likely to delay a project if not completed on time and which are less time sensitive. You can also allocate costs to each activity.

These frameworks are particularly useful when you are running a complex project, where different elements need to be carried out in parallel or with overlapping time frames.

Where did the idea of Critical Paths come from?

A guide to critical paths Critical Path Precedence Networks was first published in 1978. The author, Dr Larry Bennett, had been applying critical path theory to projects he worked on from the mid-1960s. A civil engineer and project manager, he spent almost 30 years teaching in the engineering department of the University of Alaska Fairbanks and has written several books and many papers and articles on this and related subjects.


While Critical Path Analysis and PERT Charts are invaluable for more complex projects, they can be used for any project with a variety of elements contributing to the final result.

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