“It depends” is a phrase sometimes referred to as the classic product management answer — and it is! While we all would love a simple answer to many of life’s questions, there are often many factors at play which means, well, it depends!
One factor product managers have to consider in their answers is dependencies. These activities might not be in the direct control of the product team but are required as part of the product development effort for success. No matter how best companies structure themselves to minimize dependencies, often they still exist. Finding out which ones matter and which impact timelines the most can be challenging. That is where the critical path method (CPM) can help.
What is the critical path method (CPM)?
The critical path method (CPM) is a widely-used project management technique that helps plan and schedule complex projects. It is used to identify the critical path of a project, aka the sequence of activities that determines the minimum completion time of the project.
What does “critical path” mean?
A critical path is a sequence of “critical” activities in a project that must be completed on time for the project to be completed on schedule. These “critical” activities will also help you to determine the minimum completion time for the project.
For example, if you’re building a house, the critical path might include activities like laying the foundations, building the walls, and installing the roof. All of these are needed to build a house and if any of these activities fall behind schedule, the entire project will be delayed.
What is the critical path method in project management?
The critical path method (CPM) is a tool used to plan and schedule complicated projects. It is based on identifying the critical path of a project and analyzing it to find the minimum completion time for the project.
The method considers the dependencies between different activities and the amount of time required to complete each activity. By understanding the critical path and the amount of “float” or “slack” time available in the schedule, project managers can better plan and control their projects.
A brief history of the critical path method
The Critical Path Method was first developed by Morgan R. Walker of DuPont and James E. Kelley Jr. of Remington Rand in the late 1950s. They were looking for a way to manage the complicated construction projects they were undertaking, so developed the CPM as a tool to help with this.
The method quickly gained popularity and was soon adopted by many companies and industries. Today, the CPM is widely used in project management and is considered an essential tool for planning and scheduling complicated projects.
Key terms associated with the critical path method
- Earliest start time (EST): the earliest time an activity can start, taking into account the preceding activities and their durations
- Latest start time (LST): the latest time an activity can start without delaying the project
- Earliest finish time (EFT): the earliest time an activity can be completed, taking into account the preceding activities and their durations
- Latest finish time (LFT): the latest time an activity can be completed without delaying the project
- Float or slack: the amount of time that an activity can be delayed without delaying the project
- Critical path: the sequence of activities that determines the minimum completion time for the project
How to find the critical path of a project
You can find the critical path of a project by following these steps:
- List all of the activities in the project, including their durations and dependencies
- Draw a network diagram to represent the dependencies between the activities
- Determine the earliest start time (EST) and earliest finish time (EFT) for each activity by working forwards through the network diagram
- Determine the latest start time (LST) and latest finish time (LFT) for each activity by working backward through the network diagram
- Identify the activities that have zero float (LST = EST) or negative float (LST < EST). These activities are on the critical path
When to use the critical path method
The critical path method (CPM) is an effective tool for planning and scheduling complicated projects. It is best for when the project has a large number of activities, many of which are interdependent. It’s useful when there are a lot of dependencies between different tasks and activities that must be taken into account to schedule the project effectively.
The method can also be useful when there is a desire to accurately predict the completion date for the project, or if resources need to be allocated optimally.
The CPM is generally less effective for simple projects with only a few activities, or projects where the activities are not closely dependent on each other. The method is also not a good fit for projects that have low predictability and require flexibility since the critical path is based on predetermined dependencies and durations.
The critical path method for product managers
So, if your product development is operating in a project set up and has a high number of dependencies, this tool could be useful for you and your team to better understand your dependencies and the relationship between them.
Also, while many plans are incorrect the moment you finish them, the act of planning can be useful — more useful than the plan itself. Planning gives you space to think about all the factors that will go into your successful product feature or launch and fosters communication between interested parties.
However, CPM is not suitable where there is low predictability or if flexibility is necessary. I have yet to come across a team developing software that can accurately predict how long even the smallest task takes, or that doesn’t have to deal with changing requirements. I believe most product teams operate in a complex environment, over a complicated environment where the CPM is most effective.
The Cynefin framework gives us a way of identifying the structures we operate in and identifies five domains. It covers two of the domains I reference above — the complicated and the complex.
In the complicated domain, things are more predictable and known. You can rely on best practices. Perhaps, if you are developing a product at the later end of the product lifecycle your team is in a complicated domain. However, the complex domain is novel and experimentation is necessary to work out what will be successful. If you are developing anything new you are more likely to fit into this domain and find CPM ineffective.
Conclusion
The critical path method (CPM) is a tool to plan and schedule complicated projects. It is based on identifying the critical path of a project and analyzing it to find the minimum completion time for the project.
For product managers, the analysis of what makes the critical path and consequential planning can be very helpful to foster communication and bring about a shared understanding of the activities needed for success.
However, as many teams operate in a complex, uncertain environment that requires flexibility, the CPM is unlikely to provide the answer you are probably looking for — when will it be done.
Featured image source: IconScout
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