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Michelle Symonds Discussion started by Michelle Symonds 3 years ago

Most project management software can produce a PERT (Program Evaluation and Review Technique) chart but what is it and how can a project manager use it to best effect?

A PERT chart is simply a visual representation of a project’s schedule. It is a technique rather than a tool so, in theory could be done with just pencil and paper, although in practice this is unlikely. It displays all of the project tasks and shows which ones need to be done sequentially because of inter-dependencies and which tasks can be performed in parallel to minimise the total time taken to complete the project. Importantly it also shows the critical path of activities which need to be finished on schedule for the project to stay on track.

You can create a chart with a range of attributes assigned to tasks, for example, each task can have an estimate of the least time taken to finish and the most time taken to finish. This is one of the reasons that make a PERT chart more effective than Gantt charts in that they can show a more realistic schedule of events and help the project manager manage the expectations of clients and stakeholders better. It can also help identify where potential problems could arise if one task is likely to prevent other dependent tasks from starting.

To make the best use of a PERT chart you need to identify all the tasks or activities necessary to complete the project. In the initial planning phase it is important to ensure that people with the right technical knowledge are involved so that not only are estimates realistic but to ensure that no tasks are missed off the initial schedule.

Start by getting everyone together and sequentially identify each task; at this stage it may not be necessary to break down complex tasks or tasks requiring more than one person to complete, providing the estimate is realistic but note which tasks need more detail and sub-tasks and come back to them to add detail later.

Once all the tasks are identified (don't necessarily expect to do this in one session) then you can start to look at which ones can be done in parallel to save time if you have enough people to do this. Remember that dependencies can be the result of not having adequate staff to complete tasks simultaneously; they don't have to be technical in nature.

Once you have worked through all the tasks then you need to obtain estimates for each task. Unless you have completed very similar tasks in the past these estimates will be based on the experience of the people involved and, as they are estimates, you can expect them to change, sometimes drastically, once the project is underway.

When each task has an estimate you can begin to form a schedule and add attributes such as start and end dates, and begin to determine the project's critical path. The critical path shows which tasks must start and end on schedule in order to prevent significant delays in the overall project completion. It is monitoring and controlling these critical tasks that should be the main focus of the project manager.

As with any technique and any tool, a PERT chart is not perfect but can be used in conjunction with other techniques to help you manage a project more effectively.

Replies
Paul Naybour
Paul Naybour Michelle It is interesting that what Microsoft call a PERT chart is not infact a PERT chart at all. PERT is a statistical way of calculating... Show more 3 years ago
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Michelle Symonds
Michelle Symonds Precedence Diagrams were developed after PERT charts and are more accurate at showing the relationship between different tasks so maybe that's why... Show more 3 years ago
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Paul Naybour
Paul Naybour Michelle

Precedence diagrams were developed in 1956/57 Kelly and Walker started developing the algorithms that became the ‘Activity-on-Arrow’ scheduling...
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3 years ago
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