Understanding the Critical Path

The critical path is the longest path (in time) of the whole project. The point in this distinction is because the total time it takes to complete the critical path is the time needed to complete the entire project. Alterations to the critical path will lengthen or shorten the entire project.

Steps to Implementing the Critical Path Method

There are 6 major steps to implementing the critical path method. Firstly you have to specify the activities that need to be completed. This can be done using a work breakdown structure or WBS. The idea is to identify every task in the project. This can be a hard task in itself as it can be difficult to decide what counts as a job and what should be split up into multiple jobs. It’s important to note that typically the path should be fairly high level. If the critical path has too much detail it can be hard to keep track of.

Establishing Dependencies and Activity Sequence

The second step is to establish dependencies, also known as making an activity sequence. The goal of this step is to put every job in the correct order. This is done by figuring out which jobs need to be completed before others can start. There are a number of ways to figure this out but one solid option is to ask yourself the following questions for each task on the list:

• “Which task should take place before this task happens?”

• “Which tasks should be finished at the same time as this task?”

• “Which tasks should happen right after this task?”. Asking yourself these questions can help give you an idea of when certain tasks should be done in relation to the others. This step is particularly important as the timing is the basis for what will come later.

Creating a Critical Path Analysis Chart (CPA)

Once you know the jobs and their requirements you can sketch out a critical path analysis chart (CPA) also known as the network diagram. This is just a visual representation of the data we’ve collected from the first 2 steps. It shows each task in the project connected by arrows that show dependencies. This can give an easy to understand visual representation of the essential layout of the project and the order things need to be completed in. This used to be a hand drawn process but now there is plenty of helpful software that can be used to automate this process.

Estimating Activity Completion Time

The next step is to estimate the activity completion time. This can be done using past project experiences. Talking to experienced employees or managers can help give you a better understanding of how long certain tasks may take. The scale is going to be different for every project. Jobs can be measured in days or weeks if needed. If you aren’t comfortable with your estimates you can use what’s called three point estimation to give a more accurate estimate. The basic idea is that instead of just giving one guess at the length of a job you give three. One is the best case scenario, one is the most likely scenario, the other is the worst case scenario. There are two different options next depending on the case. You can either find the average of these times or use triangular distribution. The main difference between the two is that finding the average means the time will be gravitated towards the most likely time while triangular distribution doesn’t.

Identifying the Critical Path

Your next step is to identify the critical path. This can be done by simply eyeballing the network diagram but sometimes the diagram can be fairly complex and hard to interpret. In this case you can use the Forward Pass/Backward Pass technique, finding the earliest start and finish times, and the latest start and finish times for all jobs in the project. When you have multiple critical paths the project is considered sensitive. When a project is sensitive it means that the critical path is likely to change in the middle of the project. This can obviously complicate planning and the more critical paths there are in a project the more sensitive the project is.