From the course: Project Management Simplified

The importance of your project's critical path

From the course: Project Management Simplified

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The importance of your project's critical path

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- Now we can get to the bit that we really want, the critical path. This is the longest, and therefore the slowest, path through the diagram. You can see in the diagram of my project to set up my foreign company, it goes through the permit, buying the site modifying and installing, and it adds up to a total of 34 weeks. So the critical path is just the slowest path, and the critical tasks are just the ones on the critical path. And this is really important to understand. The critical tasks aren't necessarily expensive or difficult or risky or skillful. Installing the furniture is none of those things. It just happens to be on the longest, slowest path. Originally it used to be called the time-critical path, and then project managers abbreviated it to critical path, because they talk about these things all the time. But it's quite confusing to normal people when they first come across it. Critical doesn't mean critical in the usual sense. It just means time-critical. So If something completely trivial can be on the longest path, in my example here it's installing furniture, then something really important might be a non-critical task. In my example here, it's recruiting the manager and the staff. The only way you can know what's critical is by drawing the diagram. It's all about the relationship between the tasks. You have to draw the diagram to know what's critical. You must never say, "Well, obviously the permit's "a critical task," because it might not be. Yes, it's a deal breaker, but every task is a deal breaker. Every task has to be done. But why do we care what's critical? Well, because these are the tasks that tell us how long the project's going to take, and they're also the ones that we need to watch carefully. These are the ones that make up the time scale that we have effectively promised the customer, and if they run late, the whole job runs late. The other tasks are happening in parallel, with a safety margin that's known as float, and they can go a bit late without it mattering at all. So you want to put your best people on the critical tasks and then watch them really carefully, and you want to make sure that you've estimated them correctly to start with. If your estimates are a bit out on the other tasks, it doesn't matter. In my example, getting a manager could take twice as long and it wouldn't matter, but on the critical ones they have to be correct. But we do need to keep a bit of an eye on the non-critical tasks, just in case something changes. For example, if we decide to do a task quicker, maybe we decide to spend more money on it or do it less well, something else may become our new longest path, our new critical path. So the Post-its allow us to decide on the running order in an easy way, and then they allow us to find the longest path, the critical path. I'd like you to go back to your example now and try it for yours. Can you see which path is the longest one? I'm sure you'll agree that it's easy to find and really useful to know.

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