Project management 101: The Critical Path Method

Based on previous experience, I have seen how the role of a project manager can sometimes be seen as either uneventful or non-necessary; however, a successful project manager can make, or break a project. Moreover, a successful set of tools can really change how a project runs from day one.

Project management is really a science. There are hundreds of things to learn and techniques to pick up. Having done Prince 2, (Projects in controlled environments), a project management methodology and accreditation started by the UK government to aid in the successful running of projects; I picked up little bits and peaces which definitely helped me in my time as project manager.

One of those things that I am now glad I can use in my day to day projects is the Critical Path Method. The Critical Path Method (CPM) is basically a tool for scheduling project activities and tasks. Essentially, its an easy method to help plot a sequence of activities for the project’s runtime.

Critical activities or the The Critical Path, as they are known, are those activities which basically determine the total project length (runtime, above) as well as make up the longest overall duration. If those activities are not completed on time, there is a major/real chance that the project will not meet its deadline(s).

For example, let’s give it a shot! consider a project, ‘Bob’s Health Foods Website design’ involving six tasks; A to F. The tasks have the following requirements, restrictions and time estimations.

Obviously, what the above mean for us in the long-run includes the following:

1. Tasks/activities A and B have no predecessors. What that means is that they don’t have to wait for any other task to start and/or finish before they themselves can start. That’s good news! It means we can get going on A and B right away
2. Activity C however is a little bit of a brain teaser. This activity cannot begin until activities A and B are completed.
3. Activities D, E and F also have predecessors but only one per activity.

Okay, let’s find the critical path, shall we?

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As we can see from the cool Critical Path diagram above, it all starts to make a little more sense! Our project should technically not be finished before 13 days if everything goes to plan. We calculated this by plotting the activities along a time line based on days and compared the activities in terms of any predecessors.

If an activity had a predecessor, obviously It would not be able to begin until the predecessor has run its course. This is why E, in the diagram comes right after A - because our rules stated that E cannot start until A, E’s predecessor has occurred/been completed.

Just briefly, activities such as C can be classed as having “total float”, or in layman’s terms; having the ability to be delayed without affecting the overall time line of the project. As can be seen from the critical path diagram, the path from activity C to activity F has leeway of one day! What this essentially means is that if C ran over by one day, the project would not be delayed because of the extra day between the two activities.

Having said that - if anything is delayed on the critical path; i.e. activities A and/or E, you would probably want to call it catastrophic failure (depending on the size of the project) - because it means you have just pushed your deadline! [I.e. watch out!]

Hopefully this process sinks in for you a bit more than before now. Modern project management tools like Microsoft Project can automatically work out the critical path for you - thus isolating those tasks that have to be completed on time to meet a project’s deadline. However, I must admit, it’s always a little more fun doing it yourself; especially if it’s a fairly small project!

So there you go guys, my first project management in detail article. Hopefully you are a little bit more across how the Critical Path analysis/diagram works now and how it can aid you in your next project.

Obviously the critical path is also good at helping to estimate how long a project will take in terms of dates. You’d never just tally up the individual ‘time to complete’ rows! For example, based on our project in this case, we have 6+4+5+8+7+5 = 35! Obviously our project isn’t going to take that long! Good project management, and more importantly better project planning taking into consideration Critical Path analysis will definitely aid you in getting it right!

Hope this has helped! Drop me a comment if you have any further questions, or subscribe to the RSS feed for more posts! Till next time, Cheb.