Critical path

The critical path for your project shows all the activities for your project organised so you can see when they each need to be completed, and in what order, for you to meet your project deadline.

A quick example: if you’re opening a new learning centre, the critical path will be finding a suitable room, refurbishing the room, buying IT equipment and desks/chairs, installing the equipment, and checking that everything works. Notice that these activities are in the right sequence – each is dependent on, and can only start when, the previous activity has been completed.

If you add together your time estimates for each activity, you can work out how long setting up the room will take. If your estimates are correct, this will be the shortest possible time it would take to have the room ready. So if you take longer doing any one of these activities, the overall time is increased: so if the delivery of the desks is delayed, the whole activity will run late. So in setting the date for the opening of your centre bear in mind realistic time scales. See a detailed example of a critical path map.

The other issue with critical path diagrams is that they depend on good estimates of time – and that’s notoriously tricky, and there’s no clear rule you can use. Often the best estimates are based on prior experience – has someone in your team done something similar in the past?

One option is to aim for 80% confidence in your ability to meet a deadline – e.g. you think the desks will be delivered within the week.  If you’re only about 50% sure they’ll arrive on time (maybe the same company let you down last time!) revise your time estimate. Another option is to add another 10-40% to your time estimates: the less certain you are, the more you need to increase the amount you add.