Taking the Critical Path (Part 1)

11 November, 2013

Project management is all about planning your work and working your plan. So a project manager needs to work out what needs to be done (the scope of the project) and organize the work so that it can (1) be completed as quickly as possible and (2) that it makes best use of available resources. These two activities are vital not only for successful project completion, but to pass the Project Management Professional (PMP®) exam.

Scope definition is an exercise to ensure that you have considered all activities that need to be done. It involves breaking down the overall task into logical chunks that can, in turn, be further broken down until individual activities can be identified. The Work Breakdown Structure is the favoured tool for this and it is useful to approach the breakdown from a variety of angles. You might breakdown what you are doing into important phases – obtaining planning permission, doing the ground work, laying foundations, building walls, etc. Alternatively, you can focus on the people doing the work and break down their contributions – lawyers, builders, carpenters, electricians, plumbers, etc. Once we have our scope defined, we should know what we have to do, but not when we are going to do it.

Scheduling, or Project Time Management as the Guide to the Project Management Body of Knowledge (PMBok®) calls it, is where we organize the work to take account of dependencies and constraints. The PMP® exam student will be able to recite the processes needed to prepare a schedule but even for the casual observer they are very intuitive.

Firstly, we need to ensure that the Work Breakdown Structure continues as far as activity level. According to the PMBoK®, you only need to break down work until you get to the Work Package level – a work package being a chunk of work that one person can handle, a sort of mini-project. However, there can be several weeks’ work in a Work Package, which is not ideal if you are planning a schedule. We need to break these Work Packages down into tasks (or activities as they are called in the PMP® exam) that have much shorter durations – ideally measured in hours.

Then dependencies need to be factored in. Those with PMP® certification will recognize this as the “sequence activities” process. So, for instance, we cannot build the walls before the foundations are set. Ideally what we are looking for here are activities that do not depend on each other. These can be executed in parallel – shortening the overall schedule. To continue with the building example: an electrician and a plumber can do a lot of work without interfering with each other. However, they will have to interact at certain points – wiring electric showers and earthing hot water pipes, for instance.

Identifying tasks that can be done in parallel is not sufficient for our schedule. We need to take account of the people involved. There might be a dozen plumbing tasks that can be done contemporaneously, but that is not much help if we only have one plumber. This activity will remind PMPs® of the term “resource levelling” – where the schedule is stretched out to take account of the resources available. The building example is a good case in point. Most of the tradespeople on a building site are independent sub-contractors and their own schedules might put hard constraints into our schedule. Taking account of people and other resources (such as availability of materials or equipment) is called the “estimate activity resources” process in the PMBoK®.

What this gives us is our first draft of a schedule network diagram. We lay out the tasks to reflect the dependencies and constraints we have to cope with. Next we have to estimate how long each task will take. This should be taken seriously and involve the entire project team. In fact, the PMPs® among you will recognize estimation as a team building exercise from the Project Human Resource Management knowledge area.

Three-point or PERT estimation is useful to identify risks and to make contingency explicit. If someone is asked for an optimistic estimate (the shortest possible time to do a task, assuming everything goes well), they are more likely to give a realistic figure than if they are asked for a commitment to get something done. As a project manager, you need know what constitutes time allocated for work and time allocated for mishaps – Donald Rumsfeld’s famous known-unknowns. For maximum team engagement, the Delphi approach for getting everyone’s input on the estimates allows a wider range of perspectives and more accurate estimates. Combining these two techniques (Three-point and Delphi) will allow the best of both worlds.

Now, armed with a complete list of the activities to be carried out, knowing how they should be ordered to take account of resource availability and dependencies and having estimates for each task, we can tackle the “develop schedule” process.

This will be the subject of the next article.

By Velopi Seamus Collins


© 2020 Velopi : PMBOK, PMI and the R.E.P. logo, PMP, PgMP, CAPM, PMI-SP and PMI-RMP are registered marks of the Project Management Institute, Inc.

Web Development by Granite Digital